[1406] Langerhans Cell Histiocytosis in Acute Leukemia in Adult Patients: A Unique Entity?

Sophia L Yohe, Carrie Chenault, Emina Torlakovic, Sheryl Asplund, Robert W McKenna. University of Minnesota, Minneapolis; ProPath Laboratories, Dallas, TX; University of Toronto, ON, Canada; Caris Life Sciences, Phoenix, AZ

Background: Langerhans cell histiocytosis (LCH) can precede, follow or occur concurrently with acute leukemia. When the Langerhans cell (LC) lesion occurs first, the subsequent leukemia has generally been considered treatment related. However, a clonal relationship has been demonstrated in a few cases when the Langerhans cell proliferation followed or occurred concurrently with leukemia.
Design: Four adult patients with acute leukemia (AL) and concurrent (3 cases) or subsequent (1 case) LCH were identified. Evaluation of the leukemia was performed by morphology, flow cytometry, immunohistochemistry, and/or cytogenetics. The presence of LC was confirmed by immunohistochemistry for CD1a and S100. FISH was performed on a lymph node of one patient that had trisomy 21 in the leukemic clone.
Results: One female and three male patients, ages 36 to 80 (median 61), presented with AL. Three of the four presented with synchronous LCH and AL in the bone marrow and in lymph nodes. The leukemia in these three was of an ambiguous phenotype. Two had mixed phenotype AL and one undifferentiated AL. The fourth patient presented with AML with myelodysplasia related changes and developed LCH and myeloid sarcoma in the same lymph node after consolidation chemotherapy. The LC in this case expressed CD2, CD13, and CD117 which were also expressed by the blasts. In all cases leukemic blasts and Langerhans cells were intermixed in the involved tissue. One AL case with a non-constitutional trisomy 21 in the leukemic cells also had trisomy 21 in the Langerhans cells by FISH analysis, supporting a clonal relationship between the two cell types.
Conclusions: In addition to co-mingled leukemia and LCH, these cases all had lymph node involvement by the acute leukemia and three had an ambiguous immunophenotype; three unusual features that suggest a distinct entity. Furthermore, the immunophenotypic relationship between the blasts and LC in one patient and trisomy 21 in the blasts and LC in another patient support a clonal link between the two cell types. The relationship between the two processes is speculative but could result from a common tumor stem cell or transdifferentiation of one tumor lineage to another. The presence of lymph node involvement in all four cases supports a neoplastic cell with a predilection for homing to extramedullary tissue.
Category: Hematopathology

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 235, Tuesday Morning


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