Acquisition of CD30 and CD15 accompanied with simultaneous loss of all pan-T-cell antigens in a case of histological transformation of mycosis fungoides with involvement of regional lymph node: an immunophenotypic alteration resembling classical Hodgkin lymphoma.

: Acquired expression of CD30 is frequently noted in histological transformation of mycosis fungoides (MF), but simultaneous gain of CD15 accompanied with loss of pan-T-cell antigens are extremely rare. We report an unusual case of transformed MF with such an immunophenotypic alteration resembling classical Hodgkin lymphoma. The patient was an 81-year-old male with MF, who was initially treated with topical steroids and phototherapy. Despite the initial response, the patient developed a tumor-like skin lesion that was confirmed to be CD30-positive large T-cell lymphoma and was subsequently found to have a regional lymph node involvement by pleomorphic large cell lymphoma. Besides CD30, pleomorphic large cells were positive for CD15 but negative for all B cell- and T cell-specific antigens. Epstein-Barr virus was negative. Polymerase chain reaction-based assays demonstrated a clonal rearrangement of T-cell receptor gamma gene but detected no B-cell clone. The mechanism and clinical significance of this phenotypic conversion remains to be elucidated.