Abstract

An 87-year-old man presented with several round, violaceous nodules on his anterior and posterior left leg that had been present and enlarging for one year. A punch biopsy of a distal calf lesion showed a dense dermal infiltrate of pleomorphic cells without involvement of the overlying epidermis. The neoplastic cells were positive for both B-cell antigens (CD20) and T-cell antigens (CD2, CD4, CD5) and notably negative for pan T-cell marker CD3. The cells also displayed co-expression of CD15 and CD30. Molecular studies revealed a T-cell receptor gene rearrangement. Immunoglobulin gene rearrangement was negative. A diagnosis of peripheral T-cell lymphoma (PTCL) with co-expression of CD20, CD15, and CD30 was rendered. The patient subsequently underwent a PET-CT scan that showed evidence of disseminated disease. Aberrant immunophenotypes displaying co-expression of B and T cell antigens remain a diagnostic challenge in the evaluation of lymphomas in general and present potential pitfalls in the diagnosis of cutaneous presentations of lymphomas. This rare case of PTCL with aberrant expression of CD20, CD15, and CD30 had features that suggested a B-cell or Hodgkin lineage and required an extensive immunohistochemical panel and molecular studies for eventual diagnosis. To the best of our knowledge, a cutaneous presentation of PTCL with aberrant expression of CD20, CD15 and CD30 has hitherto not been reported.