Atypical lymphoproliferative disorder-clinical and pathological features.

Definitive diagnosis of cutaneous lymphoproliferative disorders is one of the most challenging issues in dermatopathology owing to the broad spectrum of clinical and histopathological presentations. We report a case of a 73-year-old woman who presented with a single, asymptomatic plaque limited to her left collarbone. This was followed by the appearance of several plaques and patches in addition to a tumor. Her initial biopsy suggested a CD4/CD8 double negative mycosis fungoides (MF). However, the rapidly progressive course of her disease is worrisome for peripheral T-cell lymphomas-not otherwise specified (PTCL-NOS). Subsequent biopsies revealed epidermal spongiosis with subepidermal edema and possible nodal involvement by cutaneous T-cell lymphoma. The rare combination of these pathologic features demonstrates the difficulty of diagnosing atypical lymphoproliferative disorders.