Myopericytoma is an uncommon benign neoplasm that arises from the perivascular myoid cells. It typically presents as a painless well-circumscribed cutaneous or soft-tissue nodule, most commonly on the extremities of adults. Histologically, it is characterized by spindle-shaped myoid-appearing cells with a concentric arrangement in vessel walls, that are immunoreactive to alpha-smooth muscle actin and often for h-caldesmon, but negative for other smooth muscle markers. Herein, we present an unusual case of a painful subungual myopericytoma presenting as a dark subungual discoloration.

A 76-year-old woman presented to the medical oncology outpatient clinic with painful, burning, pruritic erythematous plaques involving both palms and axillae that had suddenly appeared five days before. Examination revealed no additional relevant findings and laboratory studies did not show any alteration. The patient had been recently diagnosed with a high-grade angiosarcoma of the breast (probably radiation induced) and after frequent local recurrences, was being treated with liposomal doxorubicin (three cycles were administered, the last of which was seven days before the appearance of the mentioned lesions). Oral corticosteroids were started, treatment with liposomal doxorubicin was stopped, and cutaneous biopsies performed that revealed features compatible with toxic erythema of chemotherapy induced by liposomal doxorubicin. Complete resolution of the cutaneous lesions was verified one month after. No signs of recurrence of angiosarcoma were documented at follow-up three months later.

Dermatomyositis (DM) is a systemic autoimmune disorder characterized by proximal myopathy and dermatological findings. Approximately 15-30% of DM cases emerge as a paraneoplastic syndrome caused by a concomitant malignancy. Although more rare, in cancer patients DM has also been reported as a possible result of toxicity of some antineoplastic agents, such as taxanes and monoclonal antibodies. Herein, we report a 35-year-old woman with metastatic breast cancer who presented with skin lesions after initiation of paclitaxel and anti-HER2 agents. Clinical, laboratory, and histological findings were consistent with the diagnosis of DM.