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Thymic involvement by Langerhans cell histiocytosis (LCH) has been described mainly in isolated case reports. A description of the histopathologic patterns of LCH proliferations in the thymus, together with therapeutic implications, has not, to our knowledge, been previously addressed. The pathology consultation files at Children's Hospital of Pittsburgh of the University of Pennsylvania Medical Center were reviewed for cases of thymic involvement by LCH. Relevant cases in the literature were also reviewed, and the histopathology and clinical course of those cases were collected. Nine consultation cases of thymic involvement were reviewed, together with 23 cases in the literature, which provided adequate pathologic description and ancillary confirmation (n  =  32), revealing 4 distinct pathologic groups. Group 1 showed microscopic collection of hyperplastic LCH-like cells in incidental thymectomies of patients without LCH disease, requiring no further treatment (n  =  7; 22%). Group 2 showed solitary and/or cystic LCH of the thymus with gland disruption, and at least 3 cases resolved without systemic therapy (n  =  10; 31%). Group 3 showed more variable thymic involvement in multisystemic LCH disease, with either a medullary restricted pattern or more diffuse gland involvement, requiring adjuvant therapy and having a higher mortality rate (n  =  13; 41%). Group 4 showed a mixed histiocytic lesion with a concurrent LCH and juvenile xanthogranuloma-like proliferation (n  =  2; 6%). Thymic involvement in LCH is quite rare. Based on our cases and those in the literature, we propose 4 distinct pathologic groups of thymic involvement in Langerhans cell proliferations with relevance for diagnosis and treatment.

We reviewed the experience of children with "undifferentiated" cancer at The Children's Hospital of Pittsburgh (CHP) from 1971 through 1987. Of 2,095 patients 0-18 years old with diagnoses during that time of any cancer, the initial CHP pathology report rendered a diagnosis in 22 children (1.1%) of "undifferentiated malignancy" or "malignant tumor" (15 cases), "undifferentiated carcinoma" (two cases) or "anaplastic tumor or carcinoma" not otherwise specified (five cases). A review of pathologic findings using current methods and immunostaining led to the assignment of a specific diagnosis in 15 of the 20 cases so studied. Thus, the incidence of undifferentiated cancer by current criteria was reduced to no more than 0.23%. Two of the five tumors for which an alternative diagnosis could not be established were described as "rhabdoid," but because it is not clear that these tumors fit into a single category they were still considered to be undifferentiated. Clinical features and management of the 22 cases including the five persistently diagnosed as undifferentiated malignancy were heterogeneous. In the face of reassigned diagnoses, a number of patients would likely have received different chemotherapy as well as radiation. Nonetheless, seven patients with malignancy show no evidence of disease (NED), including several whose therapy, given the current best diagnosis, would not be considered to have been optimal. We recommend that for patients undergoing biopsy of a tumor, sufficient material be obtained for extensive pathologic evaluation. In this way, the diagnosis of undifferentiated malignancy in children can be almost eliminated.(ABSTRACT TRUNCATED AT 250 WORDS)

Twenty cases of Epstein-Barr virus (EBV)-associated lymphoproliferative syndrome (LPS), defined by the presence of EBV nuclear antigen and/or EBV DNA in tissues, were diagnosed in 1467 transplant recipients in Pittsburgh from 1981-1985. The frequency of occurrence in pediatric transplant recipients was 4% (10/253), while in adults it was 0.8% (10/1214) (P less than .0005). The frequency of LPS in adults declined after 1983 coincidental with the introduction of cyclosporine monitoring. However there was no apparent decline of LPS in children. We describe these ten pediatric cases and one additional case of LPS in a child who received her transplant before 1981. The frequency of EBV infection in 92 pediatric liver recipients was 63%. Of these subjects, 49% were seronegative and 77% of those acquired primary infection. Of 11 cases of pediatric EBV-associated LPS, 10 were in children who had primary infection shortly before or after transplantation. These results reinforce the importance of primary EBV infection in producing LPS, which was previously shown in adults. Children are at greater risk because they are more likely to be seronegative for EBV and to acquire primary infection. Three clinical types of LPS were recognized in children. The first (5 cases) was a self-limited mononucleosislike syndrome. The second syndrome (4 cases) began similarly, but then progressed over the next two months to widespread lymphoproliferation in internal organs and death. The third type (2 cases) was an extranodal intestinal monoclonal B cell lymphoma, occurring late after primary infection.

Although tumors are a known complication of von Recklinghausen's neurofibromatosis (NF), they often develop after the second decade and their characteristics in the pediatric population are unclear. To define the frequency and distribution of tumor types in children with NF, the authors reviewed the experience at Children's Hospital of Pittsburgh between 1953 and 1984. During that time, 121 children younger than 18 years with documented NF were seen. Three patients (2.5%) developed locally extensive, unresectable sarcomas, two of which were clearly neural in origin. Two other children died from complications of highly cellular but not histologically malignant neurofibromas. Seventeen patients (14%) had brain tumors, of which 3 (2.5%) were malignant astrocytomas and 9 were optic gliomas. Two children had acute myelogenous leukemia. Although it has been said that patients with NF are particularly susceptible to the oncogenic effects of radiation, 12 children were treated with a median of 5000 rad to their tumor bed. Follow-up after radiation in that small cohort of patients ranged from 6 months to 12 years (mean, 6 years). Eleven of 12 patients experienced adequate local control. During the follow-up period, none developed a second tumor outside or within the radiation port that could be related to radiation. The authors conclude that clinically significant tumors in children with NF, not all of which are histologically malignant, are not rare. Although more prospective information is needed on response to and sequelae from therapy, the data in this report suggest no contraindication to aggressive therapy.