Peripheral T-cell lymphoma of Lennert type complicated by monoclonal proliferation of large B-cells

A 69-year-old man presented with lymph node swelling in the right inguinal region. A biopsy was made (LN1) and diagnosed as peripheral T-cell lymphoma. The lesion remitted completely over a period of about 51 months after combination chemotherapy, but erythematous papules, systemic lymphadenopathy, and fever of 38° appeared. Skin (S1) and lymph nodes (LN2) were biopsied. Erythematous papules once disappeared spontaneously, but appeared again and were biopsied (S2). LN1 displayed the typical histologic and immunohistochemical features of Lennert lymphoma, i.e., diffuse proliferation of small to large lymphoid cells of CD3+, CD4+, CD8− immunophenotype accompanied by numerous clusters of epithelioid histiocytes. In LN2, the large cells with CD3+, CD4+, CD8− decreased in number, while numerous CD20+ large cells were discernible. Clonality analysis revealed the persistent presence of an identical T-cell clone in LN1 and LN2. Clonal bands of immunoglobulin heavy (IgH) chain gene were detected in LN2 but not in LN1. S1 and S2 showed diffuse proliferation of small to large lymphoid cells of CD20−, CD3+, CD4+, CD8− in the upper dermis, with obvious epidermotropism. Clonality analysis revealed the presence of a T-cell clone identical to LN1 and LN2 with no B-cell clone, indicating the recurrence of PTCL. In situ hybridization (ISH) for Epstein-Barr virus (EBV) genome revealed that positive signals in the nucleus of large B-lymphoid cells appeared only in LN2.