Immunohistochemical evaluation of FLI-1 in acute lymphoblastic lymphoma (ALL): a potential diagnostic pitfall.
ABSTRACT Cases of CD45-negative acute lymphoblastic lymphoma/leukemia (ALL) immunoreactive for CD99 and Friend Leukemia Integration-1 (FLI-1) can occur and may lead to a misdiagnosis of Ewing sarcoma/peripheral neuroectodermal tumor with critical clinical treatment management implications. The objective of this study was to evaluate a panel of antibodies that would allow greater diagnostic accuracy of ALL and evaluate the frequency of FLI-1 immunoreactivity in a series of ALL cases and an expanded series of T-cell lymphoma subtypes. Immunoreactivity for CD3 was seen in 12/20 (60%), CD20 in 5/20 (25%), CD43 in 19/20(95%), CD45 in 15/20(75%), CD99 in 15/20 (75%), FLI-1, and terminal deoxynucleotidyl transferase (TdT) in 17/20 (85%) cases. Two cases negative for leukocyte common antigen (LCA), CD20, and CD3 were positive for FLI-1, CD99, TdT, and CD43. Two other LCA-negative cases were positive for CD99 but negative for FLI-1. The majority of cases showed immunoreactivity for CD43 and/or TdT. Therefore, CD43 and/or TdT should be included in the immunohistochemical evaluation of small round blue cell tumors. Absence of immunoreactivity for LCA does not exclude ALL and immunoreactivity of FLI-1 is not restricted to Ewing sarcoma/peripheral neuroectodermal tumor. We also report FLI-1 expression in an expanded series of 75 cases of T-cell lymphoma and found high expression in anaplastic large cell lymphoma and angioimmunoblastic T-cell lymphoma.
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ABSTRACT: Round cell tumors of bone are a divergent group of neoplasms that largely constitute Ewing sarcoma/primitive neuroectodermal tumor, small cell osteosarcoma, Langerhans cell histiocytosis, mensenchymal chondrosarcoma, and hematopoietic malignancies including lymphoma and plasmacytoma/myeloma, along with metastatic round cell tumors including neuroblastoma, rhabdomyosarcoma, and small cell carcinoma. These lesions share many histomorphologic similarities and often demonstrate overlapping clinical and radiologic characteristics, but typically have a diverse clinical outcome, thus warranting differing therapeutic modalities/regimens. Recent advances in molecular and cytogenetic techniques have identified a number of additional novel entities, including round cell sarcomas harboring CIC-DUX4 and BCOR-CCNB3 fusions, respectively. These novel findings have not only enhanced our understanding of the pathogenesis of round cell tumors, but also allowed us to reclassify some entities with potential therapeutic and prognostic significance. This article provides an overview focusing on recent molecular genetic advances in primary, nonhematologic round cell tumors of bone.
Article: Ewing Sarcoma[Show abstract] [Hide abstract]
ABSTRACT: Classification of small round cell tumors of bone is often challenging due to overlapping clinicopathologic features. The purpose of this article is to review the clinical, radiological, histologic, and molecular features of Ewing sarcoma and to provide a discussion of the differential diagnosis of small round cell tumors of bone.Seminars in Diagnostic Pathology 01/2014; DOI:10.1053/j.semdp.2014.01.002 · 1.80 Impact Factor
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ABSTRACT: Ewing sarcoma family of tumours are typified by small round blue cell morphology with variable but usually minimal neuroectodermal differentiation and non-random translocations involving the EWSR1 gene and a member of the ETS family of genes. Atypical morphological patterns may be seen in up to 20% of cases and include large cell, adamantinoma-like, spindle cell sarcoma-like (synovial sarcoma like), sclerosing, clear cell (hypernephroid)/anaplastic, and vascular like patterns. Immunophenotypically, CD99, vimentin, CAV1 and FLI1 are typically positive. Around half of the cases may express NSE and/or CD57. Low molecular weight cytokeratins (CK), S100, NB84, and CD117 are expressed less commonly (around 20%–40%). EMA, desmin, CD31, and synaptophysin expression are rare. CK7, CK20, D2-40, chromogranin, TDT, TTF, MYF4 appear to be consistently negative. Molecular confirmation is less sensitive. The correct diagnosis requires correlation between morphology and immunostaining, and may require molecular testing.Diagnostic Histopathology 08/2012; 18(8):348–355. DOI:10.1016/j.mpdhp.2012.06.006