A nipple-like lesion: A case report of leiomyosarcoma on the back

Leiomyosarcoma (LMS) of the skin is a rare malignant neoplasm that can have varied clinical presentations, even mimicking benign lesions, making diagnosis challenging. We describe a 74-year-old male with a history of subcutaneous LMS of the left leg treated successfully with surgery, chemotherapy, and radiation over 10 years prior, who presented with an incidental papule on the lower back resembling an accessory nipple. Biopsy revealed a spindle cell tumour with diffuse smooth muscle actin and desmin positivity and a high Ki-67 index, consistent with a non-metastatic subcutaneous LMS. Wide local excision confirmed dermal and subcutaneous involvement with negative margins. This case is notable for the occurrence of two distinct primary LMS lesions more than a decade apart, underscoring the importance of long-term surveillance in high-risk patients. Given the potential for recurrence or metastasis, careful histopathologic evaluation and ongoing monitoring remain critical in the management of LMS.