A painful nodule on the leg: a quiz. Diagnosis: Low-grade cutaneous pilar leiomyosarcoma.

Acta Derm Venereol 95 © 2015 The Authors. doi: 10.2340/00015555-2007 Journal Compilation © 2015 Acta Dermato-Venereologica. ISSN 0001-5555 A 55-year-old Caucasian farmer presented with a 1-year history of a slowly enlarging nodule on his right leg. His family history and past medical history was unremarkable. The patient believed that the lesion had been caused by accidental penetration of a foreign body into the skin. At onset, the lesion was very small and painless, but later on its size increased and it became painful. Symptoms were unresponsive to non-steroidal anti-inflammatory drugs. At physical examination, a raised reddish, mobile multinodular plaque, with irregular borders, of about 1 cm in diameter, with a small crust surrounded by a whitish scale, was evident on the anterior surface of the leg (Fig. 1). Blood tests, also including tumour markers, were negative. The lesion was surgically excised and examined histologically (Fig. 2). The lesion extended beyond the resection margins. Immunohistochemistry was positive for Desmin, Smooth Muscle Actin (SMA), and H-Caldesmon, and negative for S-100 protein, CD34, and cytokeratins