Transformed Mycosis Fungoides and Mimics: Exploring the Landscape of CD30+ Cutaneous T-Cell Lymphomas

Mycosis fungoides (MF) is an epidermotropic, primary cutaneous T-cell lymphoma (CTCL) with a generally indolent clinical course, although higher stage and transformed tumors can behave more aggressively. Large cell transformation may demonstrate CD30 expression and histologically resemble other CD30+ CTCLs, including lymphomatoid papulomatosis and cutaneous anaplastic large cell lymphoma. These entities are thought to exist on a spectrum with overlapping histologic features; however, it is of clinical importance that we do our best to accurately classify these entities due to the variability in treatment and prognosis. In this report, we present a case of CD30+ transformed MF and discuss the clues that allow us to make the challenging distinction between transformed MF and other CD30+ CTCLs. We review histologic and clinical features of these different disorders, with a focus on the revised World Health Organization classification of primary cutaneous lymphomas.