CD4/CD8 double-negative mycosis fungoides mimicking erythema gyratum repens in a patient with underlying lung cancer.

A 73-year-old Japanese man presented with a 10-year history of worsening, itchy, erythematous eruptions on his trunk and extremities. Dermatological examination revealed concentric, slightly infiltrated, annular, red patches and plaques, closely resembling EGR, on his chest, abdomen and extremities (Fig. 1). The lesions were not painful. Microscopy and culture excluded the presence of a mycotic infection. Type 1 human T-lymphotropic virus infection was also excluded. Cutaneous histopathology revealed a dense infiltrate of hyperchromatic, atypical lymphocytes that showed extensive epidermotropism. Immunohistochemical studies showed that most cells within the epidermis and dermis were CD3+, CD4–, CD8– and CD45RO+ (Fig. 2). Molecular biology investigations indicated a monoclonal rearrangement of the T-cell receptor (TCR)-beta chain. Clinical evaluation did not show spreading of TCL, but indicated primary lung adenocarcinoma. A diagnosis of Stage IB (T2N0M0B0) MF was confirmed, and treatment with cycles of photochemotherapy (psoralen plus ultraviolet A radiation; PUVA) combined with topical corticosteroids was initiated, achieving partial clinical remission. No major changes in the skin lesions were noted following surgical excision of the lung cancer.