Intermuscular leiomyoma of deep soft tissue arising in the lower chest.

Smooth muscle tumors have been traditionally divided into benign leiomyomas and malignant leiomyosarcomas. Although leiomyosarcomas arising in deep soft tissue are frequent, deep soft tissue leiomyomas other than superficial subcutaneous angioleiomyomas are uncommon, most often arising in the extremities. We report a deep soft tissue leiomyoma in the lower chest, originating between the external oblique and external intercostal muscles or ribs in a young man, a location reported only once previously.