CD8-positive granulomatous mycosis fungoides: a case report with review of the literature.

Granulomatous mycosis fungoides (GMF) represents an uncommon variant of mycosis fungoides (MF) characterized by the presence of an associated granulomatous reaction. Most cases of GMF are CD4 positive, and CD8 positive cases are extremely rare. Herein, we report a case of CD8-positive GMF. A 75-year-old Japanese woman presented with brownish maculae on the trunk and upper and lower extremities. She had been diagnosed with MF, and most of the eruption improved by psoralen ultraviolet A therapy. However, the eruption relapsed and gradually expanded 5 months prior to her visit to our hospital. Histopathology showed an atypical lymphocytic infiltrate in the dermis accompanied by granulomatous reaction with multinucleated giant cells. Epidermotropism was evident and elastophagocytosis was also found. Immunohistochemically, the atypical lymphocytes expressed betaF1, CD3 and CD8, and some of the atypical lymphocytes were also T cell intracellular antigen-1 positive. These findings were consistent with CD8-positive GMF. The dermatopathological diagnosis of GMF is challenging in some cases because of the prominent secondary granulomatous reaction. Therefore, when dermatopathologists diagnose granulomatous skin lesions, GMF should also be considered. In addition, the prognosis of GMF, especially CD8-positive GMF, is still controversial. Additional studies are required to clarify the clinicopathological features of CD8-positive GMF.