Large cell transformation mimicking regional lymphomatoid papulosis in a patient with mycosis fungoides.

A 57-year-old Japanese man with tumor-stage mycosis fungoides suddenly presented multiple small papules on the right chest. Histopathology of a biopsy specimen from the papules revealed medium-to-large pleomorphic lymphoid cells throughout the entire dermis but not in the epidermis, and the large cells expressed CD30 antigen. These newly-developed papules underwent spontaneous remission in the following 3 months. We reviewed the reported cases of mycosis fungoides, which showed CD30-positive large cell transformation and those of CD30-positive lymphoproliferative disorders associated with mycosis fungoides.