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Myxoglobulosis is a rare macroscopic form (

Diagnosis of osteocartilaginous pathologies depends on morphological examination and immunohistochemical and molecular biology analyses. Decalcification is required before tissue processing, but available protocols often lead to altered proteins and nucleic acids, and thus compromise the diagnosis. The objective of this study was to compare the effect of different methods of decalcification on histomolecular analyses required for diagnosis and to recommend an optimal protocol for processing these samples in routine practice. We prospectively submitted 35 tissue samples to different decalcification procedures with hydrochloric acid, formic acid, and EDTA, in short, overnight and long cycles for 1 to >10 cycles. Preservation of protein integrity was examined by immunohistochemistry, and quality of nucleic acids was estimated after extraction (DNA and RNA concentrations, 260/280 ratios, PCR cycle thresholds), analysis of DNA mutations (high-resolution melting) or amplifications (PCR, in situ hybridization), and detection of fusion transcripts (RT-PCR, in situ hybridization). Hydrochloric acid- and long-term formic acid-based decalcification induced false-negative results on immunohistochemistry and molecular analysis. EDTA and short-term formic acid-based decalcification (

International audience; Acral soft tissue tumors are common neoplasms, a subset of which pose a diagnostic challenge. We report 10 cases of a previously unrecognized acral benign soft tissue tumor. These tumors arose on the fingers and toes and involved bone in half of cases. Histologically, the tumors were lobulated and displayed an abundant stroma made of variable fibrous, chondroid and myxoid material reminiscent of cartilaginous or myoepithelial differentiation. Tumor cells harbored small round to reniform nuclei with clear chromatin and inconspicuous nucleoli along with scant eosinophilic cytoplasm. The cells were mostly arranged haphazardly in the stroma but also in small clusters. No mitotic activity was detected. No specific feature was identified in recurrent cases. By immunohistochemistry, the cells consistently stained for CD34 (10/10), ERG (9/10), and SOX9 (7/10). Whole RNA sequencing identified a previously undescribed recurrent in frame THBS1-ADGRF5 gene fusion in all cases. The transcript was confirmed by RT-PCR and was not found in the control group of mimickers including soft tissue chondromas. We propose the name of Acral FibroChondroMyxoid Tumors for this new entity.

A subset of benign peripheral nerve sheath tumors are "hybrid" combining several lines of differentiation, most often schwannian and perineurial features. The pathogenesis of these tumors was poorly described until the recent discovery of recurrent VGLL3 rearrangements in hybrid schwannoma/perineuriomas, supporting the hypothesis that this entity represents a distinct subgroup of tumors and not only a morphologic variation of other peripheral nerve sheath tumors. Following this finding, we investigated 10 cases of hybrid peripheral nerve sheath tumors with immunohistochemistry, RNA sequencing, and array comparative genomic hybridization. By light microscopy, 7 tumors were hybrid schwannoma/perineurioma tumors, and 3 were hybrid schwannoma/neurofibroma. Most cases of hybrid schwannoma/perineuriomas displayed VGLL3 rearrangements fused in 5' either to CHD7 or CHD9 (n=6/7) and had simple diploid genetic profiles with few copy number alterations. Compared with a control group composed of 28 tumors associated with varied neural phenotypes, all VGLL3-fused tumors clustered together by transcriptomic analysis. In contrast, 1 case of hybrid schwannoma/perineurioma tumor harbored a CDH9-ZFHX3 fusion, a prominent perineurial component identified by immunohistochemistry and clustered with perineuriomas. No recurrent genetic alteration was seen in the 3 hybrid schwannoma/neurofibromas. To summarize, this study confirms and expands the recent findings on hybrid schwannoma/perineurioma, highlighting the predominance of VGLL3 fusions in these tumors.

Myxoinflammatory fibroblastic sarcoma (MIFS) is a rare soft tissue tumor with a predilection for the distal extremities and a tendency for local recurrence. Morphologically, MIFS consists of spindle and bizarre epithelioid cells resembling virocytes embedded in a fibrous to myxoid stroma with an abundant inflammatory infiltrate. Importantly, the molecular landscape of MIFS is wide and includes: VGLL3 amplification, BRAF fusion/amplification and OGA/TGFBR3 rearrangements. In this study, we describe a variant of MIFS showing a frequent nodular configuration associated with necrosis and recurrent YAP1::MAML2 fusions. The cohort consisted of 7 patients (4 females and 3 males) ranging in age from 21 to 71 years (median: 47 years). Two tumors (28%) occurred in acral locations while the remaining cases were more widely distributed (thigh, n = 2; arm, n = 1; neck; n = 1; chest-wall, n = 1). Tumor size ranged from 10 to 38 mm (median: 20 mm). Histologically, lesions frequently presented as nodules with central areas of necrosis, and were predominantly composed of sheets of epithelioid cells with large vesicular nuclei and prominent nucleoli (Reed-Sternberg-like cells or virocytes). The stroma was mostly fibrous and showed a polymorphous inflammatory infiltrate. Myxoid stromal changes were focally seen in one case, and pseudolipoblasts were absent. The immunophenotype was nonspecific, with only pan-keratin (AE1-AE3) and cyclin D1 expression in a subset of cases. RNA-Sequencing detected YAP1::MAML2 fusions in 3/7 cases; aCGH showed no significant gene copy number variations in 4 tested cases, and FISH analysis showed no VGLL3 amplification in 1 tested case. Follow-up was available for 6 cases, ranging from 7 to 63 months (median: 42 months). Local recurrence and metastasis were not seen and one tumor showed spontaneous regression following initial biopsy. In conclusion, we describe a novel variant of MIFS with distinctive clinicopathological and molecular features for which we propose the term "nodular necrotizing" MIFS.

Nodular fasciitis, primary aneurysmal bone cyst, myositis ossificans, and their related lesions are benign tumors that share common histological features and a chromosomal rearrangement involving the ubiquitin-specific peptidase 6 (USP6) gene. The identification of an increasing number of new partners implicated in USP6 rearrangements demonstrates a complex tumorogenesis of this tumor spectrum. In this study on a series of 77 tumors (28 nodular fasciitis, 42 aneurysmal bone cysts, and 7 myositis ossificans) from the database of the French Sarcoma Group, we describe 7 new partners of the USP6 gene. For this purpose, rearrangements were first researched by multiplexed RT-qPCRs in the entire population. A targeted RNA sequencing was then used on samples selected according to a high USP6-transcription level expression estimated by RT-qPCR. Thanks to this multistep approach, besides the common USP6 fusions observed, we detected novel USP6 partners: PDLIM7 and MYL12A in nodular fasciitis and TPM4, DDX17, GTF2I, KLF3, and MEF2A in aneurysmal bone cysts. In order to try to bring to light the role played by the recently identified USP6 partners in this lesional spectrum, their functions are discussed. Taking into account that a traumatic participation has long been mentioned in the histogenesis of most of these lesions and because of their morphological resemblance to organizing granulation reparative tissue or callus, a focus is placed on their relationship with tissue remodeling and, to a lesser extent, with bone metabolism.

The infiltration by numerous osteoclastic giant cells is a frequent finding in bone tumors and pseudo-tumors. Pathologists must integrate clinical and radiological data to achieve a correct diagnosis in bone pathology. Benign giant-cell rich lesions of bone encompass giant cell tumor of bone, aneurysmal bone cyst, chondroblastoma, brown tumor and fibrous cortical defect/non-ossifying fibroma. Amongst malignant neoplasms, variants of conventional osteosarcoma, undifferentiated pleomorphic sarcoma, leiomyosarcoma and bone metastasis must be discussed. Recently, new diagnostic markers, antibodies for immuno-histochemistry and genetic markers, have been developed and are helpful to diagnose such lesions.

Denosumab, an antibody directed against receptor activator of nuclear factor-κB ligand (RANKL), has recently been introduced in the treatment strategy of giant cell tumor of bone. In this study, we assessed the tumor changes induced by denosumab in a national multicentric series of 35 cases (French Bone Pathology Group network-ResOs). Tissue specimens collected before and after denosumab treatment were investigated for RANKL, H3.3 G34W, p63, and Ki-67 expression, and for H3F3A mutation. These parameters were put in correspondance with clinical and radiologic presentation to identify prognostic factors, and more specifically, predictive markers of an optimal histologic response to denosumab, identified as a ≥50% loss in giant cells with fibrosis and ossification. The main changes in posttreatment specimens showed an induction of ossification (P=2.10), an increased fibrosis (P=3.10), and a major decrease in giant cells (P=6.10). No significant change in mononuclear tumor cell density and in patterns of expression of RANKL (P=0.061) and H3.3 G34W was observed (P=0.061). An optimal histologic response to denosumab treatment was associated with an enhanced progression-free survival (P=0.010 in univariate analyses; P=0.040 in multivariate analyses). The initial number of giant cells was predictive of the histologic response to treatment (P=0.016). In summary, denosumab treatment induced radical changes in the tumor. The histologic response, despite the absence of objective regression of the mononuclear cells, was associated with an enhanced progression-free survival. Greater numbers of giant cells represented the only predictive indication of an optimal histologic response to denosumab treatment.

International audience; Chondrosarcomas are rare primary malignant bone tumors that involve the head and neck region in 1% to 12% of cases. Central conventional chondrosarcoma is the most common subtype and is associated with isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) gene mutations in 50% to 60% of cases. We aimed to define the frequency of IDH1 and IDH2 gene mutations in a multicenter series of 88 cases of chondrosarcoma of the head and neck, including tumors involving the base of the skull (n = 30), the facial skeleton (n = 11), and the laryngeal and tracheal cartilages (n = 47). Petrous bone and cricoid cartilage were the most frequently involved sites for chondrosarcomas of the skull base and laryngotracheal tract (43.3% and 31.9%, respectively). Overall, 64.9% of craniofacial chondrosarcomas featured IDH mutations, with a high rate for skull base tumors (85.7%) but no IDH mutations in tumors of the facial skeleton. This different mutational profile could be related to the type of ossification, the bones of the base of the skull mainly resulting from endochondral ossification, and those of the face from intramembranous ossification. Conversely, mutation was infrequent in chondrosarcomas involving the laryngeal and tracheal cartilages (11.8% of 47 cases). Evaluation of IDH mutation status may be a useful diagnostic tool for bone tumors of the skull base, which are most often assessable with only small biopsy samples. The low rate of IDH mutations observed in laryngotracheal chondrosarcomas suggests a different mode of tumorigenesis needing further exploration.

To evaluate the diagnostic value of MDM2 status in craniofacial fibro-osseous lesions, we investigated MDM2 expression by immunohistochemistry and analyzed MDM2 amplification by qPCR in 30 cases of ossifying fibroma (including 13 cases of the juvenile variant) and 17 cases of fibrous dysplasia. Two cases of uncommon extragnathic psammomatoid fibrous dysplasia and a mixed control group of 15 cases of low-grade osteosarcoma and 15 cases of well-differentiated/dedifferentiated liposarcoma were included. MDM2 amplification was found in 33% of ossifying fibromas (peak of 69% for the juvenile variant) and in 12% of fibrous dysplasia, in none of which was MDM2 overexpressed. All control cases exhibited MDM2 amplification and overexpression. To investigate possible polysomy of chromosome 12, we studied RASAL1 amplification, a gene telomeric to MDM2 on the long arm of chromosome 12. RASAL1 amplification was reported in all benign fibro-osseous lesions exhibiting MDM2 amplification but not in controls. Simultaneous amplification of these two genes was significantly higher in juvenile ossifying fibromas compared with fibrous dysplasia (P=0.004), non-juvenile ossifying fibromas (P=0.001), and all other benign craniofacial fibro-osseous lesions combined (P=0.0001). Of the nine cases of juvenile ossifying fibroma exhibiting amplification, three were locally invasive and four were recurrent, suggesting aggressive disease. The two cases of extragnathic psammomatoid fibrous dysplasia also showed MDM2 and RASAL1 amplification with no MDM2 overexpression. This large chromosome 12 rearrangement, spanning MDM2 and RASAL1, is the first recurrent molecular abnormality to be reported in juvenile ossifying fibroma. It may represent both a molecular diagnostic marker and a characteristic of more aggressive forms with a higher risk of recurrence. Finally, the presence of this rearrangement in extragnathic psammomatoid fibro-osseous lesions mimicking ossifying fibromas might reflect a common molecular pathway in their pathogenesis and calls into question the classification of such lesions within fibrous dysplasia.

Some primary malignant or benign tumours of bone contain numerous multinucleated cells. These "giant cell-rich tumours of bone" have overlapping features and clinical and radiological data are needed to reach an accurate pathological diagnosis. We studied the potential contribution of p63 immunohistochemistry to the reliability of the histological diagnosis. We performed a multicentric retrospective study of 291 giant cell-rich tumours of bone which included 119 giant cell tumours of bone (GCTB), 76 aneurysmal bone cysts (ABC), 49 chondroblastomas (CB), 15 nonossifying fibromas (NOF), 10 giant cell reparative granulomas (RG) of jaws, 1 giant cell lesion of small bones, 2 hyperparathyroidism-related brown tumours (BT), 17 bone sarcomas with numerous osteoclasts and 2 malignant giant cell tumours of bone. p63 is expressed in ABC, CB, NOF, RG, BT and GCTB, but its expression in more than 50 % of mononuclear cells is strongly suggestive of a diagnosis of GCTB. In contrast, malignant GCTB were mostly negative. Our results show that p63 is expressed in a broad range of benign giant cell-rich tumours of bone, consistent with data in the recent literature, while infrequent in malignant tumours. With a cut-off 50 %, the presence of p63 positive cells is useful in supporting a diagnosis of giant cell-rich tumour of bone. However, a final diagnosis cannot be made without due consideration of all clinical/radiological and pathological data.

GNAS (guanine nucleotide-binding protein/α-subunit) mutations that induce the activation of G-protein α-subunit participate in the pathogenesis of fibrous dysplasia. The aim of this study was to evaluate the sensitivity and specificity of GNAS mutations in fibrous dysplasia and other fibro-osseous lesions, to assess the value of investigating this mutation in the diagnosis of fibro-osseous lesions. We studied 91 cases of fibrous dysplasia. The quality and/or quantity of genomic DNA were suitable for molecular analysis for 51 cases of fibrous dysplasia. GNAS mutations were investigated by three techniques: high-resolution melting (exon 8), allele-specific PCR (exons 8 and 9) and/or direct DNA sequencing (exons 8 and 9). Fibrous dysplasia samples were classified blind to the GNAS mutation status into six histological subtypes as conventional, fibro-involutive, osteosclerosing, cementifying, osteocartilaginous and with prominent aneurysmal cystic changes. We also studied 14 cases of low-grade osteosarcoma, 21 cases of ossifying fibroma, 3 cases of osteofibrous dysplasia, 1 case of osseous dysplasia of the jawbone and 1 post-traumatic lesion of the ribs. Twenty-three cases of fibrous dysplasia (45%) showed mutations of codon 201 (exon 8, p.R201H or p.R201C). No mutation was found on codon 227 (exon 9). GNAS mutations in conventional fibrous dysplasia were detected in the same proportion (47%) as in the other histological subtypes (47%, P=0.96), regardless of sex (P=0.44), age (P=0.90) and location (P=1). GNAS mutations were not detected in any other fibro-osseous lesions. The GNAS mutation was thus specific to fibrous dysplasia in the context of fibro-osseous lesions. The particular mosaicism of mutant and non-mutant cells within the lesion or the existence of other mutations not already described could explain the lack of GNAS mutation in cases of fibrous dysplasia. Investigating this mutation may constitute a valuable complementary diagnostic tool, despite its low sensitivity, particularly in unconventional morphologically different subtypes of fibrous dysplasia.

Behjati et al recently described recurrent mutations of H3F3 genes in giant cell tumors of the bone and chondroblastomas. Both these entities belong to the spectrum of giant cell-rich bone lesions, often presenting a diagnostic challenge for the pathologist. Our aim was to investigate the value of searching for H3F3 mutations in the diagnosis of giant cell tumors of the bone and giant cell-rich chondroblastomas. Two hundred eighty-one bone lesion samples, including 170 giant cell tumors of the bone, 26 chondroblastomas and 85 other giant cell-rich and/or epiphyseal tumors, were analyzed. Mutation status was determined using first high resolution melting screening and then mutation profiling pyrosequencing. Mutational status was compared with clinical data and, for giant cell tumors of the bone, with p63 immunostaining status. As histone methylation changes have been reported in association with H3F3 mutations, the methylation status of lysine 37 was investigated. H3F3A and H3F3B were found in 85% of giant cell tumors of the bone and 88% of chondroblastomas. In addition to the major G35W mutation, we found two rare H3F3A mutations: one G35R and one G35V. Among the other tumors studied, we only found H3F3A gene mutations in two cases of 'dedifferentiated chondrosarcoma mimicking giant cell tumor of the bone'. A H3F3B mutation was also observed in one case of dedifferentiated chondroblastoma. P63 expression in giant cell tumors of the bone seems to be associated with H3F3 gene mutations (P=0.004). H3F3 mutations did not correlate with clinical data, outcome or methylation changes in Lysin 37. In conclusion, H3F3 mutations are sensitive and specific markers of giant cell tumors of the bone and chondroblastomas. High resolution melting and pyrosequencing procedures are high-performance tools in this context. Determination of H3F3 mutation will allow reclassification of some entities belonging to the spectrum of giant cell-rich lesions.

International audience; Purpose Despite their functional importance, the infraspinatus (ISP) and teres minor (TM) muscles have been little investigated. This study aimed to describe the macroscopic morphology, innervation, and inter-relations of the ISP and TM muscles.Methods Forty fresh cadaver dissections and histologic analysis were performed. Three groups of specimens were distinguished according to the rotator cuff tendon status: (1) intact rotator cuff; (2) supraspinatus tendon tears with intact ISP tendon; and (3) both supraspinatus and ISP tendons torn. Muscle fiber organization and muscle and tendon length were recorded. ISP and TM innervation and fiber structure were studied.Results ISP muscles were composed of three groups of fiber organized in two planes: two superficial groups, with mean pennation angles of, respectively, 27° ± 4° and 23° ± 3° with respect to the axis of the central tendon of the underlying group. TMs were thick fusiform muscles showing a parallel organization; 26 specimens (67 %) had aponeuroses isolating the TM, with a mean length of& Guillaume Bacle bacle.guillaume@wanadoo.fr5.2 ± 2.7 cm. Rotator cuff lesions were associated with relatively greater ISP tendon than muscle length. Innerva- tion of the ISP muscle comprised 2–4 main branches from the suprascapular nerve and that of the TM 1 branch from the axillary nerve.Conclusion ISP muscle body morphology derives from three groups of fibers in two planes. The TM has a parallel organization. Several nerve branches innervate the ISP muscle, whereas only one supplies the TM. The limits between the two muscles bodies consist of an aponeurotic fascia in two-thirds of cases.

Malignant transformation of a fibrous dysplasia into an osteosarcoma is very rare. We report the case of an 84-year-old man with telangiectatic osteosarcoma of the upper femur arising in a previous fibrous dysplasia also known as liposclerosing myxofibrous tumor. The tumor was expressing the epithelial membrane antigen. This is the first described case of a malignant transformation into an osteosarcoma arising in a liposclerosing myxofibrous tumor. We discuss the main differential diagnosis with a review.

Resume Nous presentons le cas d’un rhabdomyosarcome embryonnaire de localisation orbitaire chez une femme de 51 ans, caracterise par une expression immuno-histochimique aberrante de marqueurs epitheliaux. Le rhabdomyosarcome est une tumeur rare des tissus mous atteignant principalement l’enfant, mais pouvant exceptionnellement survenir chez l’adulte apres 50 ans. Lorsqu’il se presente sous la forme d’une tumeur a petites cellules rondes, notamment dans la region tete et cou, son diagnostic peut etre difficile car un grand nombre de tumeurs peu differenciees peut etre evoque. Plusieurs cas de rhabdomyosarcome exprimant de facon aberrante des marqueurs epitheliaux ont ete rapportes dans la litterature. Un large panel d’immuno-histochimie est recommande par des etudes recentes afin d’eviter les erreurs diagnostiques. Il comprend une cytokeratine large spectre, la desmine et des marqueurs neuroendocrines, lymphoides et melanocytaires. Notre observation confirme l’importance de realiser ce panel d’immuno-histochimie incluant la desmine, devant toute tumeur peu differenciee, notamment de la region tete et cou. Cela, quel que soit l’âge du patient et meme si cette tumeur exprime des marqueurs epitheliaux.

Resume Le pronostic des osteosarcomes et des tumeurs de la famille Ewing a ete ameliore avec l’introduction de la chimiotherapie neoadjuvante. L’efficacite du traitement est evaluee en fonction du grading de Huvos et Rosen, sur l’analyse du pourcentage de cellules necrosees sur la piece de resection chirurgicale. L’evaluation du taux de cellules necrosees est le principal facteur pronostique. Il sert a adapter les protocoles de chimiotherapie. La prise en charge macroscopique et microscopique de la piece de resection chirurgicale est essentielle et fait l’objet d’un protocole specifique. De nombreuses etudes ont ete realisees pour identifier de nouvelles cibles therapeutiques. Les inhibiteurs de mTOR et/ou les regulateurs de la balance RANKL/OPG sont des molecules prometteuses en cours d’essais therapeutiques. L’etude de l’expression de nouveaux facteurs predictifs pourrait etre faite sur la biopsie des patients avant toute therapeutique neoadjuvante, et offrir la possibilite d’utiliser d’autres strategies therapeutiques.

International audience; The clinical management of osteosarcoma differs significantly from that of chondrosarcoma; therefore, it is extremely important to diagnose these 2 types of bone tumor accurately. In the absence of a specific marker, differential diagnosis by histochemistry is sometimes impossible, especially between chondroblastic osteosarcoma and conventional chondrosarcoma. We analyzed 165 bone sarcomas by immunohistochemical staining of tissue microarrays for expression of the galectin-1 (GAL1) lectin and by Western blot experiments. We found that GAL1 was abundant in normal human osteoblasts from benign proliferations and in osteosarcomas, including chondroblastic osteosarcomas, but not in chondrosarcomas. There was a highly significant statistical difference in the percentage of stained cells (P < 10(-4)) and in the staining intensity (P < 10(-3)) of chondroblastic osteosarcomas compared to conventional chondrosarcomas. This discriminatory potential of GAL1 staining for osteosarcoma-derived tumors was confirmed by Western blotting. We propose a diagnostic test for bone tumors that takes into account the optimal discriminative values for the percentage of cells stained and the intensity of staining. The positive and negative predictive values were 85.7% (trust interval of 63.7%-97%) and 90% (trust interval of 80%-95.9%), respectively, demonstrating the pertinence of the test. Altogether, our data indicate that GAL1 is a powerful diagnostic marker that distinguishes chondroblastic osteosarcomas from conventional chondrosarcomas.

Resume Nous rapportons un cas de PECome de localisation inhabituelle, intra-articulaire chez un jeune garcon de 13 ans. La tumeur, de 4 cm, mal limitee, etait composee de cellules epithelioides et fusiformes, claires ou granuleuses eosinophiles, et d’un contingent de cellules plurinucleees. Des atypies cyto-nucleaires etaient focalement observees. L’index mitotique etait evalue a 2 mitoses/50 champs au fort grandissement. Aucune necrose tumorale n’etait decelee. L’etude immunohistochimique montrait une positivite pour l’HMB45 et l’actine-muscle-lisse (AML). L’etude ultrastructurale montrait l’existence de premelanosomes. De rares cas de PEComes ont ete rapportes dans les tissus mous. Leur diagnostic repose sur la positivite des marqueurs melanocytaires (en particulier l’HMB45) et parfois de l’AML. Les criteres de malignite de ces tumeurs sont mal definis et pourraient inclure la mauvaise limitation, la taille tumorale, la presence d’atypies cytologiques et le compte mitotique. Nous discutons ici les diagnostics differentiels de cette tumeur, notamment le sarcome a cellules claires.

Specific treatments targeted toward oncogenes expressed in cancer cells are currently under development. Patients with urothelial carcinomas showing HER-2/ neu (human epidermal growth factor receptor 2) overexpression are candidates for such a specific treatment (trastuzumab). However, to be effective, this therapeutic approach requires an extremely reliable evaluation of HER-2/ neu status in tumors. In order to assess the status of expression of this gene and to optimize its assessment, we analyzed a series of 64 primary urothelial carcinomas using immunohistochemistry (IHC) with the CB11 monoclonal antibody coupled with fluorescent in situ hybridization (FISH) in 21 cases. Strong HER-2/ neu overexpression was detected using IHC in 15 of the 64 (23%) cases analyzed, and this rate rose to 33% for patients with metastases. HER-2/ neu overexpression, as revealed using IHC, is strongly associated (95%) with gene amplification assessed using FISH. Patients with urothelial carcinomas overexpressing HER-2/ neu using IHC are potential candidates for targeted chemotherapy.

International audience; In contrast to long bone osteosarcoma, mandibular osteosarcoma are highly heterogeneous and morphologically overlap with benign tumors, obscuring diagnosis and treatment selection. Molecular characterization is difficult due to the paucity of available specimens of this rare disease. We aimed to characterize the spectrum of mandibular osteosarcoma using immunohistochemistry and molecular techniques (quantitative polymerase chain reaction, sequencing) and compare them with benign fibro-osseous lesions. Forty-nine paraffin-embedded mandible osteosarcoma tissue samples were collected retrospectively and compared with 10 fibrous dysplasia and 15 ossifying fibroma cases. These were analyzed for molecular markers thought to differ between the different diseases and subtypes: MDM2 (murine double-minute type-2) overexpression; GNAS (guanine nucleotide-binding protein/alpha subunit) mutations; and amplification of MDM2 and/or RASAL1 (RAS protein activator like-1). Five fibroblastic high-grade osteosarcoma subtypes showed MDM2 amplification, including two with a microscopic appearance of high-grade osteosarcoma with part low-grade osteosarcoma (differentiated/dedifferentiated osteosarcoma) and MDM2 overexpression. The other three contained a co-amplification of MDM2 and RASAL1, a signature also described for juvenile ossifying fibroma, with no overexpression of MDM2. These were of the giant cell-rich high-grade osteosarcoma, with areas mimicking juvenile ossifying fibroma (ossifying-fibroma-like osteosarcoma). Our results show that some diagnosed high-grade osteosarcoma are differentiated/dedifferentiated osteosarcomas and harbor an overexpression and amplification of MDM2. In addition, juvenile ossifying fibromas can potentially evolve into giant cell-rich high-grade osteosarcomas and are characterized by a RASAL1 amplification (osteosarcoma with juvenile ossifying fibroma-like genotype). Thus, the presence of a RASAL1 amplification in ossifying fibroma may indicate a requirement for closer follow-up and more aggressive management

Objective.—To report the histologic and immunohistochemical features of 2 cases of intratesticular fibromatous tumors. Results.—Microscopically, these tumors were composed of short, randomly interweaving fascicles of spindle cells dispersed within a fibrocollagenous stroma. A sex cord component was detected in one case by microscopic examination and in both cases by immunohistochemical study using MIC2 and anti-inhibin antibodies. Conclusions.—The presence of minor sex cord elements, morphologically or by immunohistochemistry, suggests that these fibromatous tumors are related to and are a subset of sex cord–stromal tumors. Intratesticular fibromatous tumors, of which 11 other cases lacking sex cord elements have been reported, could be considered as the testicular equivalent of ovarian fibroma. These tumors could then be referred to as testicular fibroma of gonadal stromal origin, with or without minor sex cord component.

International audience; Low-grade osteosarcoma is a rare malignancy that may be subdivided into two main subgroups on the basis of location in relation to the bone cortex, that is, parosteal osteosarcoma and low-grade central osteosarcoma. Their histological appearance is quite similar and characterized by spindle cell stroma with low-to-moderate cellularity and well-differentiated anastomosing bone trabeculae. Low-grade osteosarcomas have a simple genetic profile with supernumerary ring chromosomes comprising amplification of chromosome 12q13-15, including the cyclin-dependent kinase 4 (CDK4) and murine double-minute type 2 (MDM2) gene region. Low-grade osteosarcoma can be confused with fibrous and fibro-osseous lesions such as fibromatosis and fibrous dysplasia on radiological and histological findings. We investigated MDM2-CDK4 immunohistochemical expression in a series of 72 low-grade osteosarcomas and 107 fibrous or fibro-osseous lesions of the bone or paraosseous soft tissue. The MDM2-CDK4 amplification status of low-grade osteosarcoma was also evaluated by comparative genomic hybridization array in 18 cases, and the MDM2 amplification status was evaluated by fluorescence in situ hybridization or quantitative real-time polymerase chain reaction in 31 cases of benign fibrous and fibro-osseous lesions. MDM2-CDK4 immunostaining and MDM2 amplification by fluorescence in situ hybridization or quantitative real-time polymerase chain reaction were investigated in a control group of 23 cases of primary high-grade bone sarcoma, including 20 conventional high-grade osteosarcomas, two pleomorphic spindle cell sarcomas/malignant fibrous histiocytomas and one leiomyosarcoma. The results showed that MDM2 and/or CDK4 immunoreactivity was present in 89% of low-grade osteosarcoma specimens. All benign fibrous and fibro-osseous lesions and the tumors of the control group were negative for MDM2 and CDK4. These results were consistent with the MDM2 and CDK4 amplification results. In conclusion, immunohistochemical expression of MDM2 and CDK4 is specific and provides sensitive markers for the diagnosis of low-grade osteosarcomas, helping to differentiate them from benign fibrous and fibro-osseous lesions, particularly in cases with atypical radio-clinical presentation and/or limited biopsy samples.

A 39-year-old woman presented with an incidentally discovered mass of the left adrenal fossa. Computed tomography and magnetic resonance imaging did not show any other lesion. Histologically, this mass was composed of a dense proliferation of spindle cells with a fibrosarcomatous-like pattern. Immunohistochemistry using anticytokeratin showed some epithelial cells within the tumor. The diagnosis of primitive synovial sarcoma of the left adrenal fossa was confirmed by the presence of the characteristic t(X;18) translocation. Despite radiotherapy, several chemotherapies, and 2 other surgical resections, the patient died 30 months after the initial diagnosis. To our knowledge, this report constitutes the first described case of synovial sarcoma arising in the adrenal gland.

Ezrin is a cytoskeleton linker protein that is actively involved in the metastatic process of cancer cells. We have recently reported that ezrin expression in conventional osteosarcoma was an independent prognostic factor for event-free survival and overall survival. In this work, ezrin expression was found in all histological subtypes. Especially cartilaginous areas in chondroblastic osteosarcomas were immunopositive for ezrin. We wanted to know if ezrin could be a useful diagnostic marker in bone pathology. We have searched for ezrin expression in 208 cartilaginous tumours by immunohistochemistry and in 16 chondroblastic osteosarcomas. All conventional chondrosarcomas, whatever their grade, were negative, while ten of 16 chondroblastic osteosarcomas were positive. In contrast, dedifferentiated (five of 14) and mesenchymal chondrosarcomas (five of ten) showed ezrin positivity. Some chondroblastomas and more rarely chondromyxoid fibromas also exhibited ezrin expression. These data suggest that ezrin is a useful immunohistochemical marker for differential diagnosis between chondroblastic osteosarcomas and conventional chondrosarcomas with a specificity of 100%. Ezrin expression in dedifferentiated and mesenchymal chondrosarcomas which are aggressive neoplasms resistant to conventional treatment means that ezrin could be a therapeutic target. Ezrin expression in chondroblastomas is more intriguing and requires further study to assess prognostic value.

Atypical lipomatous tumor/well-differentiated liposarcoma (ALT-WDLPS) and dedifferentiated liposarcoma (DDLPS) may be difficult to distinguish from benign adipose tumors and from poorly differentiated sarcomas, respectively. Genetically, they are characterized by amplification of MDM2 and CDK4 genes on chromosome 12q13-15. We examined a series of 559 soft tissue tumors (44 ALT-WDLPS, 61 DDLPS, 49 benign adipose tumors, and 405 non-ALT-WDLPS/DDLPS sarcomas) for MDM2 and CDK4 expression using immunohistochemistry. MDM2 and CDK4 immunoexpressions were compared with gene amplification status (as assessed by quantitative PCR and/or comparative genomic hybridization) in 241 neoplasms. Most ALT-WDLPS/DDLPS expressed MDM2 (97%) and CDK4 (92%) as opposed to few benign adipose tumors (MDM2, 5%; CDK4, 2%) and a limited number of non-ALT-WDLSP/DDLPS sarcomas (MDM2, 19%; CDK4, 6%). The sensitivity and specificity of MDM2 and CDK4 immunostainings in identifying ALT-WDLPS/DDLPS among other soft tissue tumors were 97% and 92%, and 83% and 95%, respectively. MDM2 and CDK4 immunostainings were particularly useful to separate ALT-WDLPS from the large group of differentiated adipose tumors, and to distinguish DDLPS from poorly differentiated sarcomas. A strong correlation was observed between MDM2 and CDK4 stainings and gene amplification status. In conclusion, MDM2 and CDK4 immunostainings, which correlate with gene amplification, are helpful adjuncts to differentiate ALT-WDLPS from benign adipose tumors and to separate DDLPS from poorly differentiated sarcomas.

In 20 sex-cord tumors of the testes, we investigated immunohistochemistry as a possible method for histopathological diagnosis and evaluation of prognosis. We examined the following molecules: inhibin, CD99, cytokeratin, vimentin, MIB-1, estrogen receptors and progesterone receptors. These tumors of the testes comprised 18 Sertoli cell tumors (ScT) and two undifferentiated sex-cord tumors (USCT). Four tumors have been considered as malignant, because of metastatic spread. Inhibin was expressed by the tumor cells in 80% of sex cord tumors, without any correlation to the degree of differentiation and only in 25% of the malignant cases. Inhibin is a specific marker for sex-cord tumors of the testis and is particularly useful for the diagnosis of USCT. CD99, vimentin, keratin, progesterone and estrogen receptors were expressed in, respectively, 60%, 75%, 35%, 65% and 20% of cases; 95% expressed one of the three following markers: inhibin, CD99 or vimentin. Proliferation index MIB-1 was equal to or higher than 30% in the four malignant cases versus less than 20% in other cases. Lack of inhibin expression and a proliferation index (MIB-1) greater than 30% should be considered as a criterion in favor of malignancy.

We report the clinical evolution of a prostate cancer, metastasizing to lungs and bones, recurring locally, and escaping from anti-androgen therapy. Key event of biological progression of the patient's tumor was the coincidence of allelic imbalance accumulation and of bone metastases occurrence. The recurrent tumor was established as the transplantable xenograft PAC120 in nude mice, where it grew locally. PAC120 displayed the same immunophenotype of the original tumor (positive for keratin, vimentin, prostatic acid phosphatase, and Leu-7) and expressed human HOXB9, HOXA4, HER-2/neu, and prostate-specific antigen genes, as detected by reverse transcriptase-polymerase chain reaction. It formed lung micrometastases detected by mRNA expression of human genes. Cytogenetic analysis demonstrated numerous alterations reflecting the tumor evolution. PAC120 was still hormone-dependent; its growth was strongly inhibited by the new gonadotropin-releasing hormone antagonist FE 200486 but weakly by gonadotropin-releasing hormone superagonist D-Trp 6 -luteinizing-hormone releasing hormone (decapeptyl). Tumor growth inhibition induced by anti-hormone therapy was linked to the hormone deprivation degree, more important and more stable with FE 200486 than with D-Trp 6 -luteinizing-hormone releasing hormone. Surgical castration of mice led to tumor regressions but did not prevent late recurrences. Transition to hormone-independent tumors was frequently associated with a mucoid differentiation or with a neuroendocrine-like pattern. Independent variations of mRNA expression of HER-2/neu and prostate-specific antigen were observed in hormone-independent tumors whereas HOXB9 gene expression was constant. In conclusion, PAC120 xenograft, a new model of hormone-dependent prostate cancer retained the progression potential of the original tumor, opening the opportunity to study the hormone dependence escape mechanism.