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The expression of the CXCR4 chemokine receptor on CD34-positive blood cells is reduced in persons with primary myelofibrosis (PMF). We analyzed the relevance of cytofluorimetric assessment of the percentage of CD34-positive blood cells that had a positive CXCR4 surface expression (CD34/CXCR4-se) in a large cohort of subjects with myeloproliferative neoplasms. Mean CD34/CXCR4-se was lower in subjects with PMF compared with those with essential thrombocythemia (ET) or polycythemia vera (PV). A cutoff value of 39% was associated with a diagnosis of pre-fibrotic PMF vs. ET with a positive predictive value of 97%. In PMF male sex, older age, and MPLmutation were independent correlates of reduced CD34/CXCR4-se and associated with a briefer interval to development of severe anemia, large splenomegaly, thrombocytopenia, leukopenia, elevated CD34-positive blood cells, blast transformation and death. We constructed a prognostic model including age >65 years, hemoglobin ?50?×?106/L, and CD34/CXCR4-se <39% at diagnosis. The model identified three risk cohorts with greater accuracy compared with the International Prognostic Scoring System. In conclusion, CD34/CXCR4-se is a highly sensitive marker of disease activity and a new potential diagnostic and prognostic biomarker in PMF.

Increased microvessel density contributes to abnormal BM and spleen microenvironment in myelofibrosis (MF). Taking advantage of the JAK2V617F mutation as a marker of malignancy, in the present study, we investigated whether splenic endothelial cells (ECs) obtained from capillaries by laser microdissection or from fresh spleen tissue by cell culture or cell sorting harbored such mutation in patients bearing the mutation in their granulocytes and undergoing splenectomy for therapeutical reasons. To extend the analysis to the ECs of large vessels, endothelial tissue from the splenic vein was also studied. We found JAK2V617F+ ECs in 12 of 18 patients also bearing the mutation in their granulocytes. In 3 patients, the mutation was found in at least 2 different EC samples obtained by laser microdissection, cell culture, or cell sorting. The mutation was detected in the splenic vein ECs of 1 of 6 patients investigated. In conclusion, we provide evidence that some ECs from the spleen and splenic veins of patients with MF bear the JAK2V617F mutation. We suggest that splenic ECs are involved in the process of malignant transformation in MF.

Increased microvessel density contributes to abnormal BM and spleen microenvironment in myelofibrosis (MF). Taking advantage of the JAK2V617F mutation as a marker of malignancy, in the present study, we investigated whether splenic endothelial cells (ECs) obtained from capillaries by laser microdissection or from fresh spleen tissue by cell culture or cell sorting harbored such mutation in patients bearing the mutation in their granulocytes and undergoing splenectomy for therapeutical reasons. To extend the analysis to the ECs of large vessels, endothelial tissue from the splenic vein was also studied. We found JAK2V617F+ECs in 12 of 18 patients also bearing the mutation in their granulocytes. In 3 patients, the mutation was found in at least 2 different EC samples obtained by laser microdissection, cell culture, or cell sorting. The mutation was detected in the splenic vein ECs of 1 of 6 patients investigated. In conclusion, we provide evidence that some ECs from the spleen and splenic veins of patients with MF bear the JAK2V617F mutation. We suggest that splenic ECs are involved in the process of malignant transformation in MF.

Posttransplantation lymphoproliferative disorders (PTLDs) are heterogeneous lymphoid proliferations representing a major complication of solid organ transplant. This study details the clinicopathological and molecular features of 17 B-cell PTLDs observed in a single center series of 988 heart and/or lung transplant recipients.

Most post-transplant lymphoproliferative disorders (PTLDs) are of B-cell origin, whereas T-cell lymphomas rarely occur. We detail the clinicopathological features of the first case of Epstein–Barr virus (EBV)-associated primary cutaneous CD30+ anaplastic large cell lymphoma (ALCL) in the setting of heart transplant. A 71-year-old patient, 111 months after transplant, presented with multiple cutaneous lesions on the left thigh; histological and immunohistochemical examinations led to diagnosis of T-cell CD30+ ALCL. In situhybridization demonstrated the presence of EBV-positive tumour cells. The patient received radiotherapy, but he relapsed at the same cutaneous site with loco-regional nodal spread. Chemotherapy was administered resulting in complete remission; four years later the patient is alive and well. Our findings indicate that primary cutaneous EBV+ CD30+ ALCLs should be included within the T-cell PTLDs spectrum; further studies are required to confirm whether they may be also considered, in transplantation settings, a distinct lymphoma subset with relatively favourable outcome.

Most post-transplant lymphoproliferative disorders (PTLDs) are of B-cell origin, whereas T-cell lymphomas rarely occur. We detail the clinicopathological features of the first case of Epstein–Barr virus (EBV)-associated primary cutaneous CD30+ anaplastic large cell lymphoma (ALCL) in the setting of heart transplant. A 71-year-old patient, 111 months after transplant, presented with multiple cutaneous lesions on the left thigh; histological and immunohistochemical examinations led to diagnosis of T-cell CD30+ ALCL. In situ hybridization demonstrated the presence of EBV-positive tumour cells. The patient received radiotherapy, but he relapsed at the same cutaneous site with loco-regional nodal spread. Chemotherapy was administered resulting in complete remission; four years later the patient is alive and well. Our findings indicate that primary cutaneous EBV+ CD30+ ALCLs should be included within the T-cell PTLDs spectrum; further studies are required to confirm whether they may be also considered, in transplantation settings, a distinct lymphoma subset with relatively favourable outcome.

Splenic and nodal marginal zone lymphomas (MZL) are subtypes of marginal zone-derived neoplasms. Due to their rarity, little is known concerning their relation, pattern of dissemination, and treatment outcome. The authors analyzed the clinicopathologic features and outcome of 43 patients (34 patients with splenic MZL and 9 patients with nodal MZL). All lesional tissues obtained at diagnosis were reviewed histologically. Among the patients with splenic MZL, 30 patients had Stage IV disease (based on the Ann Arbor staging system). Twenty-six patients presented with splenomegaly with or without limited involvement of abdominal lymph nodes, whereas 7 patients showed disease extension to superficial lymph nodes. Hepatitis C virus (HCV) serology was positive in 35% of patients. Seventeen patients underwent splenectomy, 8 patients received chemotherapy, and 7 patients were followed without initial treatment. Interferon produced a lymphoma response in three of four HCV positive patients. Of 27 treated patients, 13 patients achieved a complete response, and 12 patients achieved a partial response. The median event-free survival (EFS) was 3.3 years (5.1 years for patients with disease confined to the abdomen and 2.1 years for patients with disease extension to superficial lymph nodes). Among nine patients with nodal MZL, four patients had Stage IV disease. HCV serology was positive in two patients. Five patients responded to chemotherapy. The median EFS was 2.8 years. The median overall survival was not reached for patients with both types of MZL. The results of the current study demonstrated that splenic and nodal MZL are indolent lymphomas with different presenting features but common morphologic and biologic characteristics, including high HCV seroprevalence. Studies will be required to identify specific biologic markers and to define the best treatment. Cancer 2004;100:107–15. © 2003 American Cancer Society.

Posttransplantation lymphoproliferative disorders (PTLDs) represent a serious complication of solid organ transplantation. This study assessed the molecular histogenesis of 52 B-cell monoclonal PTLDs, including 12 polymorphic PTLDs (P-PTLDs), 36 diffuse large B-cell lymphomas (DLBCLs), and 4 Burkitt/Burkitt-like lymphomas (BL/BLLs). Somatic hypermutation (SHM) of immunoglobulin variable (IgV) genes documented that most monoclonal B-cell PTLDs (75% P-PTLDs, 91.3% DLBCLs, 100% BL/BLLs) derive from germinal center (GC)-experienced B cells. B-cell lymphoma 6 (BCL6) mutations occurred in 25% P-PTLDs, 60.6% DLBCLs, and 75.0% BL/BLLs. A first histogenetic category of PTLDs (31.2% DLBCLs) express the BCL6+/multiple myeloma oncogene-1 protein (MUM1-/+)/CD138- profile and mimic B cells experiencing the GC reaction, as also suggested by ongoing SHM in a fraction of these cases. A second subset of PTLDs (66.7% P-PTLDs and 31.2% DLBCLs) display the BCL6-/MUM1+/CD138- phenotype and mimic B cells that have concluded the GC reaction. A third histogenetic category of PTLDs (25.0% P-PTLDs and 31.2% DLBCLs) shows the BCL6-/MUM1+/CD138+ profile, consistent with preterminally differentiated post-GC B cells. Crippling mutations of IgV heavy chain (IgVH) and/or IgV light chain (IgVL) genes, leading to sterile rearrangements and normally preventing cell survival, occur in 4 DLBCLs and 1 BL/BLL that may have been rescued from apoptosis through expression of Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1). Overall, the histogenetic diversity of monoclonal B-cell PTLDs may help define biologically homogeneous categories of the disease. (Blood. 2003;102: 3775-3785)

Posttransplantation lymphoproliferative disorders (PTLDs) represent a serious complication of solid organ transplantation. This study assessed the molecular histogenesis of 52 B-cell monoclonal PTLDs, including 12 polymorphic PTLDs (P-PTLDs), 36 diffuse large B-cell lymphomas (DLBCLs), and 4 Burkitt/Burkitt-like lymphomas (BL/BLLs). Somatic hypermutation (SHM) of immunoglobulin variable (IgV) genes documented that most monoclonal B-cell PTLDs (75% P-PTLDs, 91.3% DLBCLs, 100% BL/BLLs) derive from germinal center (GC)-experienced B cells. B-cell lymphoma 6 (BCL6) mutations occurred in 25% P-PTLDs, 60.6% DLBCLs, and 75.0% BL/BLLs. A first histogenetic category of PTLDs (31.2% DLBCLs) express the BCL6+/multiple myeloma oncogene-1 protein (MUM1-/+)/CD138-profile and mimic B cells experiencing the GC reaction, as also suggested by ongoing SHM in a fraction of these cases. A second subset of PTLDs (66.7% P-PTLDs and 31.2% DLBCLs) display the BCL6-/MUM1+/CD138-phenotype and mimic B cells that have concluded the GC reaction. A third histogenetic category of PTLDs (25.0% P-PTLDs and 31.2% DLBCLs) shows the BCL6-/MUM1+/CD138+profile, consistent with preterminally differentiated post-GC B cells. Crippling mutations of IgV heavy chain (IgVH) and/or IgV light chain (IgVL) genes, leading to sterile rearrangements and normally preventing cell survival, occur in 4 DLBCLs and 1 BL/BLL that may have been rescued from apoptosis through expression of Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1). Overall, the histogenetic diversity of monoclonal B-cell PTLDs may help define biologically homogeneous categories of the disease. (Blood. 2003;102: 3775-3785)

May-Hegglin anomaly, Sebastian syndrome, Fechtner syndrome, and Epstein syndrome are autosomal dominant macrothrombocytopenias distinguished by different combinations of clinical and laboratory signs, such as sensorineural hearing loss, cataract, nephritis, and polymorphonuclear Döhle-like bodies. Mutations in the MYH9 gene encoding for the nonmuscle myosin heavy chain IIA (NMMHC-IIA) have been identified in all these syndromes. To understand the role of the MYH9 mutations, we report the molecular defects in 12 new cases, which together with our previous works represent a cohort of 19 families. Since no genotype-phenotype correlation was established, we performed an accurate clinical and biochemical re-evaluation of patients. In addition to macrothrombocytopenia, an abnormal distribution of NMMHC-IIA within leukocytes was observed in all individuals, including those without Döhle-like bodies. Selective, high-tone hearing deficiency and cataract was diagnosed in 83 and 23, respectively, of patients initially referred as having May-Hegglin anomaly or Sebastian syndrome. Kidney abnormalities, such as hematuria and proteinuria, affected not only patients referred as Fechtner syndrome and Epstein syndrome but also those referred as May-Hegglin anomaly and Sebastian syndrome. These findings allowed us to conclude that May-Hegglin anomaly, Sebastian syndrome, Fechtner syndrome, and Epstein syndrome are not distinct entities but rather a single disorder with a continuous clinical spectrum varying from mild macrothrombocytopenia with leukocyte inclusions to a severe form complicated by hearing loss, cataracts, and renal failure. For this new nosologic entity, we propose the term “MHY9-related disease,” which better interprets the recent knowledge in this field and identifies all patients at risk of developing renal, hearing, or visual defects.

Background:Fechtner syndrome (FTNS), also known as Alport-like syndrome, is a rare inherited condition characterized by progressive nephritis, macrothrombocytopenia, Döhle-like leukocyte inclusions, deafness, and cataract. Although it recently was shown that FTNS derives from mutation of MYH9, the gene for the heavy chain of nonmuscle myosin IIA (NMMHC-IIA), its pathophysiological characteristics remain unknown. Methods:We studied a large FTNS family in which 10 components carried a missense mutation of MYH9determining the D1424H substitution. Results:All affected subjects presented with macrothrombocytopenia and leukocyte Döhle-like bodies consisting of macroaggregates of NMMHC-IIA, but only two subjects had major renal problems characterized by proteinuria and renal failure. Electron microscopy showed focal and segmental effacement of podocytes and loss of the interpodocyte slit diaphragm. Immunohistochemistry showed apical localization of NMMHC-IIA in tubular epithelia and less podocyte staining in the two patients, whereas it was diffuse in normal epithelia. Three patients presented with stable microhematuria, and another five patients had no renal lesions, although they carried the same mutation of MYH9. Therefore, MYH9mutation per se was responsible for platelet and leukocyte abnormalities, whereas additional predisposing conditions and/or environmental factors are necessary for nephropathy, cataract, and deafness. Looking at podocyte components conferring permselectivity properties to the kidney, we characterized the haplotype of podocin and found cosegregation of one specific allele in the two patients with nephrotic syndrome, suggesting a relationship between podocin features and proteinuria. Conclusion:Our study indicates a major role for the NMMHC-IIA abnormality in the pathogenesis of leukocyte, platelet, and kidney defects in FTNS. The basic feature in all cases is aggregation and compartmentation of NMMHC-IIA. However, proteinuria and podocyte lesions are the hallmark of nephropathy in patients who develop renal failure, and podocin may have some function in this setting. Am J Kidney Dis41:95-104. © 2003 by the National Kidney Foundation, Inc.

In 1981 Weemaes et al. first described the Nijmegen breakage syndrome (NBS), a rare autosomal recessive disorder characterized by stunted growth, microcephaly, immunodeficiency, spontaneous chromosome instability, and a peculiar predisposition to cancer development. Most NBS-related malignancies are lymphomas, but their pathologic features have rarely been specified. We report here the case of a northern Italian 8-year-old child who, 2 years after the diagnosis of NBS, developed a diffuse large B-cell lymphoma (T cell–rich B-cell lymphoma variant). The histological and immunobiological features of the lymphoma population are analyzed and discussed in detail.

Thirty adult patients with lymphoblastic lymphoma were treated with two different programs according to bone marrow findings. Bone marrow positive patients were given an ALL-like program: vincristine, daunorubicin, cyclophosphamide and prednisone for induction of remission, CNS prophylaxis, continuous maintenance for three years and monthly reinductions. Bone marrow negative patients were given a conventional lymphoma program with CHOP-Bleo and limited RT on bulky mediastinum without CNS prophylaxis. The CR rate of the whole group was 54 % (62 % for ALL-treated versus 47 % for lymphoma-treated patients; not significantly different), with a median survival for remitters of 28.5 mos. Relapse-free survival of the whole group was 65 % at 12 and 25 % at 24 mos. Stage IV ALL-treated patients had a median survival of 16.5 versus 10 mos for stage IV lymphoma-treated ones (p = 0.05); the three-years survival was 24 and 10 %, respectively. No patients undergoing CNS prophylaxis (ALL-therapy) had neurological complications or late meningeal relapse. The better prognosis of ALL-treated patients, in spite of bone marrow positivity, argues in favor of an ALL-like therapy in all adult lymphoblastic lymphomas, in terms of CR rate, overall survival, and absence of CNS relapse. This therapy must be adopted irrespective of bone marrow findings, and regardless of how localized the lymphoma appears to be.

We reviewed 182 consecutive adult patients with low-grade malignancy, non-Hodgkin's lymphomas classified according to the Kiel classification, followed at the Division of Hematology, Policlinico S. Matteo, Pavia, from January 1975 to December 1981, to recognize, in each histopathologic type, important subgroups from the prognostic standpoint. Median follow-up was 36 months. No significant differences were observed in the response rate to conventional therapy (radiotherapy for localized disease, CVP for advanced stages) between the 4 cytologic types. The centrocytic-centroblastic lymphoma with diffuse nodal architecture showed an intermediate-grade malignancy (median survival, 50 months) and underwent cytologic progression to the high-grade malignancy centroblastic type in 10% of the cases. Large-cell centrocytic and polymorphic lymphoplasmacytoid lymphomas had a poor prognosis (median survival less than 30 months) when treated with conventional therapy for favorable histologies, and 6% of the cases transformed into the high-malignancy immunoblastic type. Patients with lymphocytic lymphoma with bulky mediastinum had a median survival of 20 months. The identification of these subgroups with a worse prognosis may have therapeutic implications.

Cutaneous and visceral dissemination of Kaposi's sarcoma (KS) occurred in a patient with angioimmunoblastic lymphadenopathy with dysproteinemia (AILD) who had been treated with combination chemotherapy. Three other cases of KS complicating immunosuppressive therapy of AILD have been reported in the literature, and there is evidence to indicate that AILD displays features which are known to predispose to KS. Like in other subjects with profound immunodeficiency (e.g. in young homosexual men), in our patient KS pursued an unusually aggressive course, with involvement of lymph nodes and internal organs as well as the skin. It is concluded that the risk of developing severe KS is a further reason to avoid aggressive combination chemotherapy in patients with AILD, particularly in those of Jewish or Mediterranean ancestry. Even the use of corticosteroids should be reduced to a minimum to avoid immunosuppression, and a conservative approach to treatment seems advisable.

The t(2;5)(p23;q35) translocation associated with CD30-positive anaplastic large cell lymphoma results in the production of a NPM-ALK chimeric protein, consisting of the N-terminal portion of the NPM protein joined to the entire cytoplasmic domain of the neural receptor tyrosine kinase ALK. The ALKgene products were identified in paraffin sections by using a new anti-ALK (cytoplasmic portion) monoclonal antibody (ALKc) that tends to react more strongly than a previously described ALK1 antibody with the nuclei of ALK-expressing tumor cells after microwave heating in 1 mmol/L ethylenediaminetetraacetic acid buffer, pH 8.0. The ALKc monoclonal antibody reacted selectively with 60% of anaplastic large cell lymphoma cases (60 of 100), which occurred mainly in the first three decades of life and consistently displayed a T/null phenotype. This group of ALK-positive tumors showed a wide morphological spectrum including cases with features of anaplastic large cell lymphoma “common” type (75%), “lymphohistiocytic” (10%), “small cell” (8.3%), “giant cell” (3.3%), and “Hodgkin's like” (3.3%). CD30-positive large anaplastic cells expressing the ALK protein both in the cytoplasm and nucleus represented the dominant tumor population in the common, Hodgkin's-like and giant cell types, but they were present at a smaller percentage (often with a perivascular distribution) also in cases with lymphohistiocytic and small cell features. In this study, the ALKc antibody also allowed us to identify small neoplastic cells (usually CD30 negative) with nucleus-restricted ALK positivity that were, by definition, more evident in the small cell variant but were also found in cases with lymphohistiocytic, common, and “Hodgkin's-like” features. These findings, which have not been previously emphasized, strongly suggest that the neoplastic lesion (the NPM-ALK gene) must be present both in the large anaplastic and small tumor cells, and that ALK-positive lymphomas lie on a spectrum, their position being defined by the ratio of small to large neoplastic cells. Notably, about 15% of all ALK-positive lymphomas (usually of the common or giant cell variant) showed a cytoplasm-restricted ALK positivity, which suggests that the ALK gene may have fused with a partner(s) other than NPM. From a diagnostic point of view, detection of the ALK protein was useful in distinguishing anaplastic large cell lymphoma cases of lymphohistiocytic and small cell variants from reactive conditions and other peripheral T-cell lymphoma subtypes, as well as for detecting a small number of tumor cells in lymphohemopoietic tissues. In conclusion, ALK positivity appears to define a clinicopathological entity with a T/null phenotype (“ALK lymphomas”), but one that shows a wider spectrum of morphological patterns than has been appreciated in the past.

Paraffin-embedded lymph node biopsies from 107patients with newly diagnosed non-Hodgkin's lymphomas were examined for cell DNA content and proliferative activity (as percentage of S-phase cells) by means of flow cytometry. Patients were diagnosed between 1975and 1985and were homogeneously treated according to the grade of histologic malignancy. Cytofluorimetric data were studied with regard to their correlation with histology (classified and reviewed according to both Kiel and Working Formulation criteria), clinical stage, presence of constitutional symptoms, presence of bulky disease, sex, age, and the following laboratory data measured at diagnosis: erythrocyte sedimentation rate, hemoglobin, serum lactic dehydrogenase and serum albumin concentration. Aneuploidy was more frequent in the high grade malignant subtypes and in the miscellaneous group but showed no correlations with the other clinical parameters studied. Proliferative activity demonstrated a wide variation of data but a trend was evident toward higher proliferative values in the more severe histologic subtypes. The survival discrimination allowed by high- and low-grade malignant histology is exactly reproduced when highly and slowly proliferating lymphomas are considered (> or ⩽ 12%of S-phase cells).

A 16-year-old boy with congenital hepatic fibrosis, on whom a portocaval anastomosis was performed because of bleeding esophageal varices, developed lip cyanosis, exertional dyspnea, and clubbing of the fingers 7 years postoperatively. This progressive syndrome was caused by a right-to-left shunt due to the presence of pulmonary arteriovenous fistulas. Increased erythrocyte sedimentation rate, hypergammaglobulinemia, and histological features of cholangitis were also present. It is proposed that this unusual pulmonary complication of congenital hepatic fibrosis could be due either to congenital pulmonary abnormalities or to a chronic unrecognized cholangitis causing a progressive deterioration of liver histology and function, with subsequent opening of pulmonary arteriovenous shunts.

Fifty-eight patients with immunoblastic lymphoma (IBL) were the object of this study. Fifteen of them (26 %) developed IBL during or after other diseases, either immunologic or neoplastic, including angio-immunoblastic lymphadenopathy, autoimmune disorders, chronic lymphocytic leukemia, Waldenström's disease, lymphoplasmacytoid lymphoma and Hodgkin's disease (subsequent IBL). The comparison between de novo and subsequent IBL revealed a significantly higher incidence of bone marrow involvement and bulky abdominal disease in the latter group, with a lower response rate to chemotherapy. The favorable primary extranodal disease of Waldeyer's ring exclusively belonged to de novo IBL, whereas the frequency of immunoglobulin abnormalities was higher in the subsequent IBL group (67 %). The stage of disease, systemic symptoms at diagnosis and response to therapy were predictive of survival. The overall complete remission (CR) rate in the whole series was 37 % and the median overall survival 14 months. Complete remitters have a median survival in excess of 60 months; all relapses occurred within the first 12 months of CR. No CNS relapse terminated the CR, and CNS prophylaxis seems unnecessary in IBL. The analysis of subsequent IBL may provide information on the pathogenesis of non-Hodgkin's lymphomas; the still poor prognosis of IBL deserves new therapeutic attempts to improve on the standard regimens.

Heart lesions induced in mice, rats, rabbits and dogs by Doxorubicin administered i.v. according to various schedules were studied by light and electron microscopy. Vacuolization of myocardial cytoplasm due to distention of the sarcoplasmic reticulum, the T-tubule system and the Golgi vesicles was one of the most common findings. Myocytolysis, clumping and loss of fibrils, fragmentation of sarcomeres, swelling of mitochondria and an increase in lysosomes and residual bodies were also observed. The severity of the cardiomyopathy, quantitatively evaluated by a score system, proved to be dose-dependent. Cardiomyopathy was more severe when the treatment was given in a short period by administration of high doses than when the same cumulative dose was administered as low doses repeated for a long period. The left atrium was more severely affected than the ventricles when high doses were given, whereas it was less affected in animals given low doses. The cardiomyopathy was less severe in animals receiving the same dose in a high volume of solvent and during a long perfusion time. Threshold doses were needed both to induce the cardiomyopathy and to establish it as a progressive disease.

In rats repeatedly treated subcutaneously as infants with adriamycin in 2 cycles of 4 treatments each, the induction of ocular and dental abnormalities and tumors was studied. Cataracts appeared from 18 to 26 days in 80 % of CD rats treated with 1.15 mg/kg/day of adriamycin and from 28 to 104 days in 55 % of Wistar-Lewis rats given 0.75 mg/kg/day adriamycin. Abnormal growth of incisors was observed in 30 % of the CD rats and in 44 % of the Wistar-Lewis rats. At lower doses, no such abnormalities were found. At about 1 year after treatment, 100 % of the CD rats treated with 0.75 mg/kg/day adriamycin and about 60 % of the Wistar-Lewis rats treated with 0.75 and 0.5 mg/kg/day adriamycin developed tumors, which were histologically classified.

We evaluated the presenting clinical characteristics and outcome of 68 patients with nodular lymphocyte predominance Hodgkin's disease (NLP-HD), in order to delineate the pattern of evolution of the disease. The male to female ratio was 46/22 and median age 35 yrs (range, 14-86). Eight patients had a history of benign hyperplasia on lymph node biopsies performed 6 to 36 months before the diagnosis of NLP-HD. Early stage disease accounted for 75% of cases. One patient had a coexistent non-Hodgkin's lymphoma (NHL). Treatment was as follows: radiotherapy in 26, chemotherapy in 23, combined modality in 19. CR rate was 93% (63/68). 18 patients relapsed as HD and 5 developed NHL. The cumulative risk of NHL was 9% at 10 yrs. During remission, 4 patients had 5 episodes of follicular hyperplasia histologically documented. Overall survival rate was 71% at 10 yrs and and 63% at 15 yrs. Freedom from progression (FFP) declined from 67% at 5 yrs to 45% at 10 yrs, because of late relapses. Localized disease predicted for a better FFP (p = 0.01), but was not associated with a reduced risk of recurrence over time.NLP-HD is characterized by an indolent course with a constant pattern of relapse over time, also in patients with early stage disease at diagnosis. In addition to relapse as NLP-HD, patients may evolve into a NHL or develop benign lymph nodal hyperplasia. Careful long-term follow up is needed for these patients.

A 16-year-old boy with congenital hepatic fibrosis, on whom a portocaval anastomosis was performed because of bleeding esophageal varices, developed lip cyanosis, exertional dyspnea, and clubbing of the fingers 7 years postoperatively. This progressive syndrome was caused by a right-to-left shunt due to the presence of pulmonary arteriovenous fistulas. Increased erythrocyte sedimentation rate, hypergammaglobulinemia, and histological features of cholangitis were also present. It is proposed that this unusual pulmonary complication of congenital hepatic fibrosis could be due either to congenital pulmonary abnormalities or to a chronic unrecognized cholangitis causing a progressive deterioration of liver histology and function, with subsequent opening of pulmonary arteriovenous shunts.

No relevant conflicts of interest to declare.

An important issue in myeloproliferative diseases research is to test the hypothesis that in the neo-angiogenesis, which is observed in the spleen and bone marrow of patients, involves endothelial cells derived from the neoplastic clone. In this study we analyzed the gene expression profile of 138 genes in CD34+ hematopoietic cells from the spleen and peripheral blood of patients with myelofibrosis (MF) and healthy individuals (HI). These genes have been selected among those that characterize the neoangiogenic gene signature or belonging to deregulated expression pathways in MF, and are listed in Table1.

No relevant conflicts of interest to declare.

Background. Extensive neoangiogenesis is a distinctive feature of both the spleen and the bone marrow (BM) of patients with myelofibrosis (MF). We and others have previously reported that mature endothelial cells obtained from microvessels of the spleen, either by laser microdissection or by cell sorting, harbor the V617FJAK2 mutation, whereas nothing is known about the existence of such mutated endothelial cells in the BM. The origin of the mutated endothelium has not been clarified up to now, although it has been proposed that it could derive from the transdifferentiation of a mutated CD34+ hematopoietic progenitor cells into an endothelial cell, an event similar to what already observed in solid tumors. Aim. To assess the presence of the V617FJAK2 mutation in mature endothelial cells from the BM of patients with MF and to evaluate the presence of transitional cells expressing both myeloid and endothelial cell markers in the BM of MF patients. Patients and Methods. Paraffin-embedded BM sections from 5 patients with MF, harboring a V617FJAK2 mutation in their granulocytes, were used both for isolating mature endothelial cells by laser microdissection and for immunostaining with antibodies directed against CD34, CD33, and CD144 (VE-cadherin) antigens. Sections from patients with lymphomas who underwent a BM biopsy for staging of the disease were used as controls (n=2). The images were obtained by confocal laser scanning microscopy (Olympus Fluoview FV10i, 60x objective) and processed by IMAGE J software. DNA was extracted from 50 microdissected endothelial cells by a commercial kit and the presence of V617FJAK2 mutation assessed by an allele-specific real-time quantitative PCR. Results. The V617FJAK2 mutation was detected in at least 1 sample of endothelial cells of 5/5 patients, indicating that a mutated endothelium, in addition to the spleen, is also detectable in the BM of patients with MF. The allelic burden ranged from 51.4% to 84.1% of mutated alleles, and was similar to the allelic burden of hematopoietic cells in 1 case, whereas it was lower in 4. Staining of BM sections from 4 patients with antibodies specific for hematopoiesis (CD33) and endothelium (VE-cadherin), as well as common to the 2 lineages (CD34), while confirming the presence of increased neoangiogenetic processes in samples from MF patients, allowed the detection of cells, usually located close to neovessels, co-expressing both hematopoietic (CD33, CD34) and endothelial (VE-cadherin, CD34) markers. These "triple positive" cells were found in all the slides of all patients whereas they were never observed in the BM sections of controls. Conclusions. V617FJAK2 positive endothelial cells can be detected in the BM of patients with MF, similarly to what observed in the spleen. These mutated endothelial cells could derive from the transdifferentiation of hematopoietic mutated cells as suggested by the detection of cells co-expressing both myeloid and endothelial markers. These observations support the hypothesis that the endothelial lineage is involved in the process of malignant transformation of MF, providing new perspectives in our understanding of the phenotype, evolution, and therapy of the disease.

Two patients with Beckwith-Wiedemann syndrome have recently been reported1 with adrenal calcifications that were presumed to be a consequence of unrecognized adrenal hemorrhage. We describe a patient with Beckwith-Wiedemann syndrome in the neonatal period with a massive hemorrhage of the right adrenal gland. To our knowledge, no other cases of confirmed bleeding into the adrenals have been reported in patients with this syndrome.Report of a Case.—A male infant born after normal labor, with a birth weight of 3.7 kg, was transferred to the University of Pavia (Italy) Pediatric Department on the first day of life because of intense cyanosis, tachypnea, and macroglossia. On admission, an umbilical hernia, ear lobe anomaly, and hemihypertrophy were noted. The liver was palpable 3 cm below the right costal margin, and two round masses, thought to be enlarged kidneys, were palpable in each flank. A grade 3/6 systolic murmur was present. Laboratory

No relevant conflicts of interest to declare.

Prefibrotic myelofibrosis (pre-MF) is a prodromic variant of primary myelofibrosis (PMF) characterized by prevalence of female sex, young age, high frequency of splanchnic vein thrombosis and indolent disease course (Barosi et al, PLoS One. 2012;7(4):e35631). Here we report the molecular characteristics at diagnosis of 177 consecutive pre-MF patients included in the institutional data-base of PMF patients at the Center for the Study of Myelofibrosis in Pavia from January 2001 through July 2013. As compared with patients with fibrotic type-MF (bone marrow (BM) fibrosis= 1 to 3), the frequency of JAK2V617F mutation in pre-MF patients (BM fibrosis=0) was higher (69.2% vs. 60.9%; P=0.02) but the JAK2V617F allele burden was lower (39% vs. 50.6%; P=<0.001). Patients with pre-MF displayed MPL, EZH2 or ASXL1 mutation at a frequency of 2.6%, 0% and 0% respectively, lower than in fibrotic type-MF (frequency: 7.6%, 4%, 17.4%, respectively). Both 45/1 haplotype of the JAK2 gene (rs12343867), and A3669G polymorphism of the glucocorticoid receptor (GR)- rs6198, known susceptibility alleles for PMF, were over-represented in pre-MF with respect to the normal control population (minor allele frequency, 43.3% vs. 24%, and 22.5% vs. 18.2%, respectively; P<0.001 and P= 0.04, respectively). However, the frequency of the variants were not significantly different in pre-MF with respect to fibrotic type-MF (minor allele frequency, 43.4% vs. 46.9%, and 22.5% vs. 27.1%). In pre-MF JAK2V617F mutated patients, a significant correlation between the burden of the V67F allele and the frequency of 46/1 haplotype (rs 12343867) was documented. By dividing JAK2V617F mutated patients in quartiles of allele burden, the frequency of the minor C allele increased progressively from 0.29% to 0.71% (P<0.001, X2 test for trend). No association was ascertained between the burden of the V617F allele and G allele of CR A3669G polymorphism. In conclusion, pre-MF patients segregated preferentially with JAK2V617F mutated genotype with low allele burden. Pre-MF patients were characterized by an almost complete absence of the acquired somatic mutations (EZH2 and ASXL1) that complement the JAK2V617F mutation in the fibrotic type-MF, and that are known to be associated to poor survival and propensity to blast transformation. Pre-MF patients were associated with susceptibility alleles 46/1 and GR A3669G, and the strength of association was not different from that of the fibrotic type-MF patients.

WHO diagnostic criteria of myeloproliferative neoplasms (MPNs) identify a preMF variant including patients having absence or early grade fibrosis, dual myeloid and megakaryocytic dominance, and clusters of atypical, ectopic, variable in size megakaryocytes in the bone marrow (BM). Many issues on the variant are critical, such as its distinction from essential thrombocythemia, recognisability, biological identity and true place among MPNs. Here we describe the clinical presentation of patients with preMF collected among a large cohort of patients diagnosed with PMF according WHO and for whom long-term follow-up data were available. The aim is to investigate whether there is an underlying structure of the patients' characteristics that allows to assign them to a distinct variant of MPNs or to align them along a continuum in the realm of PMF.We included in this study patients with PMF who were referred to the Center for the Study of Myelofibrosis of IRCCS Policlinico S. Matteo Foundation, Italy from 1990 to 2011. In all patients the BM biopsy taken at diagnosis was reviewed (pathologist: UM) and the diagnosis of preMF was established adopting the stringent criterion that, besides typical BM cellularity and megakaryocyte morphology, BM had less than grade 1 reticulin fibrosis (EUMNET criteria).Of the 659 patients with PMF, 126 fulfilled the criteria we established for the diagnosis of preMF, thus accounting for 19.1% of the cohort. Female sex accounted for 59.5% of the preMF cohort while it accounted for 33.8% of PMF fibrotic type (P<0.0000). The mean age at diagnosis of patients with preMF was 39.2 years (range, 6 to 78 years), while it was 54.6, range 6 to 90 years (P<0.0000) in patients with PMF fibrosis type. Patients with preMF showed higher hemoglobin (14.0 vs. 11.9 g/dL; P=0.0004), higher platelet count (647 vs. 435 × 109/L; P<0.0000), lower WBC count (9.0 vs. 10.7 x109/L; P=0.02) and smaller spleen index (120 vs. 182; P<0.0000) than patients with MF fibrotic type. As a consequence, preMF displayed a greater frequency of patients with grade 0 IWG prognostic score ( 88.7% vs. 56.9%, P<0.0000). PreMF patients displayed a higher frequency of thrombotic events at the time of the diagnosis or in the year preceding the diagnosis (30.1% vs. 6.4%; P<0.0000). Both in prefibrotic and fibrotic type MF, the great majority of the thrombotic episodes were portal vein thrombosis or Budd-Chiari syndrome (89.4% in preMF and 79.4% in PMF fibrotic type). The proportion of JAK2 V617F mutated patients was not significantly different in the two categories of patients (65.2% vs. 62.1%; P=NS).In order to assign patients with PMF to groups with different degrees of BM fibrosis, we further categorized MF fibrotic type into early MF (BM fibrosis grade 1) and advanced MF (BM fibrosis grade 2 or 3). Female frequency steadily varied from 59.5% to 43.2% and 25.6% in the 3 categories of BM fibrosis, respectively. Age varied from 39.2, 50.4, 57.0 years, respectively. Hemoglobin and platelet count steadily decreased (Hb=14.0, 13.3, 11.2 g/dL, respectively; platelet count=647, 554, 346 x109/L, respectively). Spleen size steadily increased along with increasing of BM fibrosis (spleen index=120, 152, 200). All these parameters exhibited a statistically significant trend along the continuum of BM fibrosis grade (ANOVA, P<0.0001). During 993 cumulative person-years of follow-up, 4% of patients with preMF died. During 1372 cumulative person-years of follow-up, 15.4% of patients with early MF died. During 1446 cumulative person-years of follow-up, 24.5% of patients with advanced MF died. The cause of death was blast transformation in 80, 53 and 41.7% of cases, respectively. 94%, 80% and 54% of patients with preMF, early MF and advanced MF were alive at 10 years from the diagnosis. Overall, these results speak in favour to preMF belonging to a continuum of epidemiological, clinical and histological phenotypes in the realm of PMF. Splanchnic vein thrombosis, on the contrary, clusters in the category of preMF, suggesting that young age, female sex and a very indolent hematological phenotype are associated with biological characteristics that predispose to thrombosis.The BM picture of preMF identifies a group of patients with PMF associated with a very indolent hematologic phenotype, female dominance and very young age at presentation characterized by high incidence of splanchnic vein thrombosis.Barosi: Novartis: Membership on an entity's Board of Directors or advisory committees.

Abstract 1743

High mobilization into peripheral blood of putative endothelial progenitor cells (EPCs) has been proposed as a characteristic of primary myelofibrosis (PMF) among the myeloproliferative neoplasms (MPNs). Endothelial colony forming cells (ECFCs) are a distinct colony type with robust proliferative potential and vessel forming capacity in vivo, and candidates to represent true EPCs. Low number of circulating ECFCs, however, imposes analytical work out in order to use this measurement as a feasible biological indicator of EPC mobilization. Here we report the assessment of ECFCs in patients with MPNs, based on a high number of patients in order to characterize the MPN categories and patients' clinical phenotype that better correlate with such measurement.One hundred thirty nine patients with PMF, 32 patients with essential thrombocythemia (ET) or polycythemia vera (PV) and 22 normal subjects were studied. ECFCs were grown in vitro by plating mononuclear cells, obtained from 40 ml of peripheral blood, onto collagen treated culture plates in the presence of EGM-2MV medium, according to Ingram et al (Blood, 2004). Medium was changed every 3 days. Plates were scored for the presence of ECFC every 2 days, starting from 10 days of culture and up to 28 days. JAK-2V617F mutation was assessed on patients granulocytes by semi-nested PCR.Patients with PMF had a significant higher (p<0.5) median frequency of ECFCs in peripheral blood (0.48 ECFC/10 ml, range 0–6) with respect to normal subjects (0.14, range 0–0.5) and patients with ET (0.25, range 0–1) or PV (0.13, range 0–0.57). Frequency was higher (p<0.05) in patients with prefibrotic PMF (0.86 ECFC/10 ml; n=36) than in patients with fibrotic PMF (0.41/10 ml; n=103). A history of previous splanchnic vein thrombosis (SVT) was associated to statistically higher (p<0.01) ECFC frequency (1.45 ECFC/10 ml; n=21) compared to patients without thrombosis (0.46/10 ml; n=118), as well as to healthy subjects, either with or without history of thrombosis (0.29 and 0.14, respectively, p<0.05 for both). At univariate analysis, increased expression of circulating ECFCs in PMF was associated with younger age (r = − 0.22, p<0.02), diagnosis of prefibrotic myelofibrosis (r = 0.72, p<0.01) and history of splanchnic vein thrombosis (r = 0.68, p<0.001). No correlation was found with the JAK-2 mutational status. At multivariate analysis all the three characteristics maintained an independent association. Since there was no association between the frequency of circulating ECFCs and the time from the onset of SVT, and since patients with an idiopathic SVT had marginal increase in ECFCs frequency compared to healthy subjects, we favored the hypothesis that an increased frequency of circulating ECFC is associated with the myeloproliferative phenotype more than with thrombosis per se. Finally, in the whole population of patients, a direct relationship (r= 0.71, p< 0.02) between the frequency of circulating ECFCs and the index of vascular splenomegaly (spleen index / number of circulating hematopoietic CD34+ cells) was evidenced.Increased mobilization into peripheral blood of ECFCs is a distinctive and new biomarker of prefibrotic myelofibrosis. In addition, this study addresses to the hypothesis that mobilization of ECFCs in MPNs is associated with high risk of SVT and with increased vasculature in the spleen, suggesting a potential role for EPCs in neoangiogenetic processes in this organ.No relevant conflicts of interest to declare.

Abstract 309>

A gain-of-function mutation of the Janus kinase 2 (JAK2) gene has been recently reported in patients with polycythemia vera (PV), essential thrombocythemia (ET) and chronic idiopathic myelofibrosis (CIMF) [N Engl J Med. 2005 Apr 28;352(17):1779–90]. Abnormal trafficking of CD34-positive cells with increased numbers in the peripheral blood is found in CIMF and in advanced stages of other myeloproliferative disorders. To determine whether the unique JAK2 V617F mutation affects the mobilization of CD34-positive cells into peripheral blood, we studied the relationship between JAK2 mutation status, bone marrow and circulating CD34-positive cells in 72 patients diagnosed according to the WHO criteria. A quantitative real-time polymerase chain reaction (PCR)-based allelic discrimination assay was used for the quantitative detection of the JAK2 V617F alleles in circulating granulocytes. Bone marrow CD34-positive cells were quantitatively assed on paraffin immunostained sections, while circulating CD34-positive cells were enumerated by flow cytometry using a single-platform assay. Overall, 57% of the patients studied carried the JAK2 V617F mutation. Within these patients, median values for JAK2 V617F alleles in circulating granulocytes were as follows: 29% in PV, 4% in ET, 12% in prefibrotic CIMF, 27% in fibrotic CIMF, and 99% in post-PV myelofibrosis. The vast majority of circulating granulocytes were homozygous for the mutation in all but one of patients with post-PV myelofibrosis. Decreased numbers of bone marrow CD34-positive cells and increased counts of circulating CD34-positive cells were detected in patients with fibrotic bone marrow. The higher the degree of fibrosis, the higher the circulating CD34-positive cell count (P<0.001) and the lower the bone marrow CD34-positive cell count (P<0.01). All patients with PV, ET and prefibrotic CIMF, and 7 out of 21 patients with fibrotic CIMF had circulating CD34-positive cell counts lower than 10 x 106/L. Conversely, all patients with post-PV myelofibrosis had counts higher than 10 x 106/L. In univariate analysis, there was an inverse relationship between percentage of JAK2 V617F alleles and bone marrow CD34-positive cells (r=−0.35, P<0.01), and a direct relationship between percentage of JAK2 mutant alleles and circulating CD34-positive cells (r=0.46, P=0.001). Multivariate analysis showed that disease category (P=0.0008) and percentage of JAK2 V617F alleles (P=0.03) were independently related to circulating CD34-positive cell counts. These observations suggest that the JAK2 V617F mutation might be involved in the constitutive mobilization of CD34-positive cells into peripheral blood that is found in patients with myeloproliferative disorder. Nonetheless, constitutive mobilization is present in a considerable portion of patients who do not carry the JAK2 mutation, pointing to additional pathogenetic mechanisms. Findings on patients with PV suggest that transition form heterozygosity to homozygosity for JAK2 V617F may represent an important step in the progression of PV to myelofibrosis. Thus, sequential evaluation of the percentage of JAK2 mutant alleles and enumeration of circulating CD34-positive cells may be useful for disease monitoring in PV.

An aberrant tyrosine kinase signalling due to non-receptor tyrosine kinase JAK2 V617F mutation has been highlighted in the pathogenesis of polycythemia vera (PV). In myelofibrosis with myeloid metaplasia (MMM) this mutation has been reported to be present in approximately 50% of the patients and its pathogenetic role is not elucidated. Here we report the results of JAK2 V617F mutation in a retrospective analysis of blood samples from 170 patients with MMM. Search for JAK2 mutation was performed by an allele specific PCR from DNA purified from granulocytes. To evaluate whether the mutation was carried in the homozygous or heterozygous state, digestion of PCR products with BsaXI restriction enzyme was performed. The overall frequency of JAK2 V617F mutation was 60% and homozygosity for the mutation was found in 39.2% of mutant samples. Disease duration was similar in JAK2 mutated and wild type patients. Patients who harboured an homozygous mutation had an higher myeloproliferative severity score (that indexed leukocytosis, thrombocytosis and splenomegaly) than patients who had a wild type or heterozygous genotype. In post-PV MMM, the mutant gene was present in 22/22 (100%) of patients, and the frequency of homozygosity was 59% of the mutated cases. In post-ET MMM (n=13), the mutant gene was present in 46% of the patients, and the frequency of homozygosity was 16% of the mutant samples. In idiopathic MMM (n=135), the incidence of the mutational state was 54.8%, with 35.1% of homozygote mutation. Patients who had received a diagnosis of prefibrotic myelofibrosis (WHO classification) had an incidence of the mutation significantly lower than patients who were diagnosed in the fibrotic stage (6/18, 33% vs 68/112, 60.7%; P=0.001). By considering only patients not receiving cytoreductive or disease modifying agents, patients who had an heterozygote mutation, had a mean Hb value higher than wild type patients (9.4 g/dL vs. 11.4 g/dL; P=0.004). Moreover, patients who had an homozygote mutation had the myeloproliferative severity score higher than both heterozygote and wild type patients (2.26 vs 1.59, P=0.008, and 2.26 vs.1.52, P=0.001, respectively). We conclude that JAK2 V617F mutation is significantly represented in MMM patients. It is a necessary event in the transformation from PV to MMM while not in the transformation from ET to MMM. Patients who harboured an heterozygote state maintained higher Hb values than patients with a wild type genotype, while the homozygote mutation was associated with leukocytosis, thrombocytosis and splenomegaly.

An aberrant tyrosine kinase signalling due to non-receptor tyrosine kinase JAK2 V617F mutation has been highlighted in the pathogenesis of polycythemia vera (PV). In myelofibrosis with myeloid metaplasia (MMM) this mutation has been reported to be present in approximately 50% of the patients and its pathogenetic role is not elucidated. Here we report the results of JAK2 V617F mutation in a retrospective analysis of blood samples from 170 patients with MMM. Search for JAK2 mutation was performed by an allele specific PCR from DNA purified from granulocytes. To evaluate whether the mutation was carried in the homozygous or heterozygous state, digestion of PCR products with BsaXI restriction enzyme was performed. The overall frequency of JAK2 V617F mutation was 60% and homozygosity for the mutation was found in 39.2% of mutant samples. Disease duration was similar in JAK2 mutated and wild type patients. Patients who harboured an homozygous mutation had an higher myeloproliferative severity score (that indexed leukocytosis, thrombocytosis and splenomegaly) than patients who had a wild type or heterozygous genotype. In post-PV MMM, the mutant gene was present in 22/22 (100%) of patients, and the frequency of homozygosity was 59% of the mutated cases. In post-ET MMM (n=13), the mutant gene was present in 46% of the patients, and the frequency of homozygosity was 16% of the mutant samples. In idiopathic MMM (n=135), the incidence of the mutational state was 54.8%, with 35.1% of homozygote mutation. Patients who had received a diagnosis of prefibrotic myelofibrosis (WHO classification) had an incidence of the mutation significantly lower than patients who were diagnosed in the fibrotic stage (6/18, 33% vs 68/112, 60.7%; P=0.001). By considering only patients not receiving cytoreductive or disease modifying agents, patients who had an heterozygote mutation, had a mean Hb value higher than wild type patients (9.4 g/dL vs. 11.4 g/dL; P=0.004). Moreover, patients who had an homozygote mutation had the myeloproliferative severity score higher than both heterozygote and wild type patients (2.26 vs 1.59, P=0.008, and 2.26 vs.1.52, P=0.001, respectively). We conclude that JAK2 V617F mutation is significantly represented in MMM patients. It is a necessary event in the transformation from PV to MMM while not in the transformation from ET to MMM. Patients who harboured an heterozygote state maintained higher Hb values than patients with a wild type genotype, while the homozygote mutation was associated with leukocytosis, thrombocytosis and splenomegaly.

A gain-of-function mutation of the Janus kinase 2 (JAK2) gene has been recently reported in patients with polycythemia vera (PV), essential thrombocythemia (ET) and chronic idiopathic myelofibrosis (CIMF) [N Engl J Med. 2005 Apr 28;352(17):1779–90]. Abnormal trafficking of CD34-positive cells with increased numbers in the peripheral blood is found in CIMF and in advanced stages of other myeloproliferative disorders. To determine whether the unique JAK2 V617F mutation affects the mobilization of CD34-positive cells into peripheral blood, we studied the relationship between JAK2 mutation status, bone marrow and circulating CD34-positive cells in 72 patients diagnosed according to the WHO criteria. A quantitative real-time polymerase chain reaction (PCR)-based allelic discrimination assay was used for the quantitative detection of the JAK2 V617F alleles in circulating granulocytes. Bone marrow CD34-positive cells were quantitatively assed on paraffin immunostained sections, while circulating CD34-positive cells were enumerated by flow cytometry using a single-platform assay. Overall, 57% of the patients studied carried the JAK2 V617F mutation. Within these patients, median values for JAK2 V617F alleles in circulating granulocytes were as follows: 29% in PV, 4% in ET, 12% in prefibrotic CIMF, 27% in fibrotic CIMF, and 99% in post-PV myelofibrosis. The vast majority of circulating granulocytes were homozygous for the mutation in all but one of patients with post-PV myelofibrosis. Decreased numbers of bone marrow CD34-positive cells and increased counts of circulating CD34-positive cells were detected in patients with fibrotic bone marrow. The higher the degree of fibrosis, the higher the circulating CD34-positive cell count (P<0.001) and the lower the bone marrow CD34-positive cell count (P<0.01). All patients with PV, ET and prefibrotic CIMF, and 7 out of 21 patients with fibrotic CIMF had circulating CD34-positive cell counts lower than 10 x 106/L. Conversely, all patients with post-PV myelofibrosis had counts higher than 10 x 106/L. In univariate analysis, there was an inverse relationship between percentage of JAK2 V617F alleles and bone marrow CD34-positive cells (r=−0.35, P<0.01), and a direct relationship between percentage of JAK2 mutant alleles and circulating CD34-positive cells (r=0.46, P=0.001). Multivariate analysis showed that disease category (P=0.0008) and percentage of JAK2 V617F alleles (P=0.03) were independently related to circulating CD34-positive cell counts. These observations suggest that the JAK2 V617F mutation might be involved in the constitutive mobilization of CD34-positive cells into peripheral blood that is found in patients with myeloproliferative disorder. Nonetheless, constitutive mobilization is present in a considerable portion of patients who do not carry the JAK2 mutation, pointing to additional pathogenetic mechanisms. Findings on patients with PV suggest that transition form heterozygosity to homozygosity for JAK2 V617F may represent an important step in the progression of PV to myelofibrosis. Thus, sequential evaluation of the percentage of JAK2 mutant alleles and enumeration of circulating CD34-positive cells may be useful for disease monitoring in PV.