0Mycosis fungoides with CD30-positive cells in the epidermis

Large numbers of CD30-positive tumor cells are not typically observed in my cosis fungoides (MF), but CD30 expression may occur on large cells of MF th at have transformed into high-grade large cell lymphoma. Of 202 patch/plaqu e phase MF cases studied by immunohistochemistry, we encountered 4 patients with patch-phase MF at stage la or Ib, whose lesions contained a high prop ortion (greater than 50%)) of CD30-positive tumor cells within the epidermi s. The morphologic and immunohistochemical features of these four cases wer e otherwise similar to those of other patch-phase MF cases, and were differ ent from those of pagetoid reticulosis. More importantly, the clinical beha vior of these cases did not differ from that of other cases of early MP wit hout CD30 expression. The mechanism underlying the high levels of CD30 expr ession by epidermotropic tumor cells is unknown. With increased use of the CD30 immunohistochemical stain in the diagnosis of cutaneous lymphomas, sim ilar cases are likely to be encountered, and perhaps will be evaluated for their clinical behavior.