274 Unexpected Morphology of Lymphomatous Adult T-cell Leukemia/Lymphoma in an Afro-Caribbean Patient

Introduction/Objective Adult T-cell Leukemia/Lymphoma (ATLL) is a rare, aggressive neoplasm of mature T-cells caused by human T-lymphotropic virus type 1 (HTLV-1). ATLL typically shows pleomorphic morphology (small, medium, large cells) and rarely presents with anaplastic or angioimmunoblastic features with variable immunophenotype. These rare patterns pose diagnostic challenges, mimicking other aggressive lymphomas and correlating with worse survival outcomes. We present an aggressive case of lymphomatous ATLL with rare morphology resembling Hodgkin/Reed-Sternberg and Anaplastic Large Cell Lymphoma. Methods/Case Report A 79-year-old Afro-Caribbean woman presented with syncope, anemia (Hemoglobin 5.6 g/dL), and leukocytosis (WBC 14.02 K/uL). Imaging revealed splenomegaly and generalized lymphadenopathy. Inguinal lymph node biopsy showed diffuse effacement by pleomorphic medium to large cells, some binucleated while others have horseshoe-shaped nuclei. Immunophenotyping was positive for CD30 (CD15-), CD25, and CD4, negative for CD3, CD5, CD7, Pax5, CD10, CD8, EMA, and ALK. Ki-67 was 80%. EBER-ISH was negative. TCR gene-rearrangement confirmed a monoclonal T-cell population. HTLV-1 serology was positive. The patient succumbed to her illness shortly after diagnosis. Results NA Conclusion This case highlights the diagnostic challenge of ATLL with anaplastic/Hodgkin-like features. ATLL should remain in the differential diagnosis of T-cell lymphomas, supported by HTLV-1 testing. Early recognition is critical given the disease’s aggressiveness and limited treatment options.