Emilie Holder

An otherwise healthy man in his 80s presented with a rapidly enlarging solitary plaque on the forearm. Physical examination revealed an isolated erythematous, telangiectatic plaque, firm to palpation (Figure 1A). Dermoscopy showed an erythematous telangiectatic lesion, suggestive of a dermal proliferative process. No additional lesions were identified on full-skin examination. Histopathologic examination demonstrated a highly cellular, dermal-based neoplasm composed of a spindle-cell proliferation.

Kaposi sarcoma (KS) is an angiogenic tumor of lymphatic endothelial origin associated with human herpesvirus 8 (HHV-8) infection. It is most commonly observed in immunocompromised patients, including those with HIV or following transplant. Mogamulizumab, an anti-CCR4 monoclonal antibody, is indicated for the treatment of primary cutaneous T-cell lymphomas (CTCLs) after failure of prior therapy. Here, we report 2 cases of KS emerging in the setting of mogamulizumab treatment.