Uterine smooth-muscle tumor of uncertain malignant potential metastasizing to the humerus as a high-grade leiomyosarcoma.

BACKGROUND: Smooth-muscle tumors of uncertain malignant potential represent a variant of uterine leiomyoma and remain a dilemma due to their uncertain clinical behavior. Most of these tumors have a benign clinical course, and coagulative tumor cell necrosis has usually been associated with worse outcome.

CASE: We present a case of a uterine smooth-muscle tumor (SMT) of uncertain malignant potential without coagulative tumor cell necrosis that has metastasized to the humerus. The metastatic lesion was a high-grade leiomyosarcoma consistent with uterine origin.

CONCLUSIONS: Smooth-muscle tumors of uncertain malignant potential that demonstrate a lack of coagulative tumor cell necrosis do not necessarily insure benign clinical outcome. These lesions can recur and metastasize to distant sites, thus requiring long-term follow-up.