TUMORS WITH SMOOTH-MUSCLE DIFFERENTIATION

BACKGROUND. In the classification of tumors of soft tissue, modern sch emes describe tumors by the normal adult tissue type the tumor resembl es. Thus, tumors are described as smooth muscle tumors if the cells ar e differentiating towards smooth muscle. We may infer that in fact the tumor arose from smooth muscle, but this is only an inference. Tumors showing differentiation towards smooth muscle include hamartomas, ben ign tumors, and malignant tumors. OBJECTIVE. This review article descr ibes the clinical presentation and course, histology, and treatment re commendations for benign and malignant smooth muscle tumors. METHODS. An extensive literature review of tumors with differentiation towards smooth muscle. RESULTS. Benign tumors exhibiting differentiation towar ds smooth muscle include smooth muscle hamartoma and leiomyoma, Myofib roma is a third tumor that some have argued is it smooth muscle tumor rather than a fibroblastic tumor. Characteristic fusiform shaped cells with a round central nucleus arranged in fasicles suggest smooth musc le differentiation. Special stains such as phosphotungenistic acid-hem otoxilin, analine blue, and Masson's trichrome are helpful in differen tiating muscle from collagen. Immunohistochemical stains are also help ful in establishing a diagnosis. With solitary tumors, treatment for c osmesis or for painful leiomyomas is not a problem. Multiple leiomyoma s, which may be painful or sensitive to cold or touch, are a therapeut ic challenge, with reports of multiple medications being attempted in the literature. Leiomyosarcoma are malignant tumors of smooth muscle. They may be cutaneous and presumably arise from the arrector pilorum m uscle, or subcutaneous, where they are believed to arise from vascular smooth muscle. Cutaneous leiomyosarcomas frequently reoccur following excision, but rarely metastasize. Subcutaneous leiomyosarcomas freque ntly reoccur following excision and have a high metastatic rate. Sever al recent reports have documented an increased frequency of visceral l eiomyosarcomas in immunosuppressed patients. These tumors have been fo und to contain the Epstein Barr virus. Treatment of leiomyosarcoma is wide excision. CONCLUSIONS. Smooth muscle tumors are rare neoplasms th at may confront the dermatologic surgeon. While leiomyomas are benign, their frequent sensitivity or pain necessitates treatment. Leiomyosar comas are malignancies with a high reoccurrence rate, and when deep, a high metastatic rate. The finding of an increased frequency of viscer al leiomyomas and leiomyosarcomas in immunosuppressed patients may imp ly an increased frequency of cutaneous leiomyomas and leiomyosarcomas in this patient population.