#00066185

A 53-year-old male with a prior diagnosis of hemophagocytic lymphohistiocytosis presented with abdominal distension, shortness of breath, and pedal edema. PET/CT demonstrated splenomegaly with findings suspicious for a lymphoproliferative disorder. Complete blood counts revealed anemia (hemoglobin 8.9 g/dL), thrombocytopenia (platelets 17 × 10⁹/L), WBC count of 9.35 × 10⁹/L, and approximately 30% atypical lymphoid cells on smear.

Bone marrow aspirate was hypercellular with diffuse infiltration by approximately 81% atypical lymphoid cells. These cells were pleomorphic, medium to large in size, with a high nuclear-to-cytoplasmic ratio, basophilic cytoplasm with vacuolations, fine chromatin, and prominent nucleoli; occasional cells showed polar cytoplasmic projections (Figure 1 and 2). Trephine biopsy showed 80–85% cellularity with diffuse marrow infiltration.

Immunohistochemistry demonstrated diffuse positivity for CD3, CD56, and CD99, with negativity for TdT, CD34, MPO, PAX5, EBV, ALK, CD30, CD4, CD5, and CD8. Flow cytometry on bone marrow aspirate identified an abnormal CD45-bright, low side-scatter population expressing CD56, HLA-DR, and CD38, and lacking T-cell, B-cell, myelomonocytic, and immaturity markers. Morphologic, immunohistochemical and flow cytometric findings were consistent with diagnosis of peripheral T/NK-cell lymphoma extensively involving the bone marrow