Peripheral T-cell lymphoma with aberrant expression of CD30, CD15, and CD20.

Case Report A 72-year-old male presented with slowly growing submental and inguinal lymph nodes for the previous 3 months. A biopsy of the submental lymph node was performed, and flow cytometric analysis showed a predominant population of cells positive for CD3, CD5, dim CD7, and CD20 and negative for CD4, CD19, and surface immunoglobulin. The lymph node architecture was effaced by atypical cells of varying size arranged in cords and large sheets. These cells had irregular nuclear contours, vesicular chromatin, and occasional prominent nucleoli. Rare bizarre cells and occasional Reed-Sternberg-like cells were seen (Fig 1A). Mitotic figures were abundant. The background contained small lymphocytes and histiocytes, but no eosinophils or neutrophils were appreciated. According to immunohistochemistry, the neoplastic cells were positive for CD20 (Fig 1B), CD2 (subset), CD3 (Fig 1C), CD5, CD30 (subset; Fig 1D), CD15 (subset; Fig 1D inset), MUM1, and CD45. The cells were negative for CD79a, PAX5 (Fig 1B inset), CD4, CD8, TIA1, granzyme B, CD56, ALK1, and in situ hybridization for Epstein-Barr virus (EBV) – encoded RNA. Molecular studies for immunoglobulin gene rearrangement showed a polyclonal rearrangement pattern (Figs 2A and 2B; PC, polyclonal; IGH, immunoglobulin heavy chain gene; FR2, framework 2; FR3, framework 3). T-cell gene rearrangement studies showed two intense peaks consistent with a clonal process (Fig 2C; TRG, T-cell receptor gamma gene rearrangement). A diagnosis of peripheral T-cell lymphoma (PTCL) with aberrant expression of CD30, CD15, and CD20 was rendered. The patient was treated with 6 cycles of R-CHOP (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone) and a follow-up positron emission tomography scan (5 months) showed no evidence of residual disease. However, 4 months later, he relapsed with recurrent disease in the skin. Interestingly, the neoplastic cells had become CD4 positive but negative for CD20, likely as a result of therapy with rituximab. This case highlights pitfalls in the accurate diagnosis of PTCL as the expression of CD20 might lead one to suspect a B-cell neoplasm, whereas the expression of CD30 and CD15 point toward diagnosis of classical Hodgkin’s lymphoma (cHL).