OBJECTIVETo study the clinicopathologic features, immunophenotype and molecular genetic changes of T lymphoblastic lymphoma (T-LBL) associated with Langerhans cell histiocytosis (LCH).

METHODSThree cases of T-LBL associated with LCH were included. The morphologic characteristics were reviewed along with immunohistochemical profiling using EnVision method and TCR gene rearrangement by PCR. A review of composite lymphoma previously reported in the literature was performed.

RESULTSAll three patients were male with the mean age of 61.7 years. One was Hans and the other 2 were Uyguers. All presented with superficial lymph node enlargement. Biopsy of lymph node showed two abnormal cell populations: distended sinus by large, pale histiocytes with nuclear grooves, and the interfollicular region containing immature-appearing cells with irregular nuclei slightly larger than that of small lymphocyte, dispersed chromatin, inconspicuous nucleoli, scant cytoplasm, and scattered mitotic figures. These cells presented in aggregates and small sheets interspersed with normal-appearing lymphocyte. The histiocytes were positive for CD1a, S-100 protein and CD68. The lymphoma cells were positive for CD3, CD7, TdT and CD34. TCR-γ gene rearrangement was detected in one case by PCR technology. One case involved bone marrow with double phenotype acute leukemia. Amongst the 8 including 5 reported cases, there were 4 males and 4 females. The mean age of the patients and the median age were 54 years. Lymphoadenopathy was the most common presentation. Bone marrow was involved in 4 cases. The time of follow-up was 2 to 27 months. The median survival was 5.5 months and the one-year survival rate was 33.3%.

CONCLUSIONSDiagnosis of T-LBL and LCH should be based on typical morphology, immunophenotype and molecular genetic findings, with differential diagnoses including Langerhans cell hyperplasia originated from dermatopathic lymphadenopathy. When involving lymph node, extensive sampling supplemented by immunohistochemical staining is important to reach a correct diagnosis. Although coexistent T-LBL and LCH is clonally related, the understanding of its pathogenesis requires further investigation.