We describe a 56-year-old female with absence of the right pectoralis muscles, aplasia of the right breast, and skeletal deformities of the right hand, typical of Poland's syndrome. Following complaints of lower abdominal pain, a CT examination revealed an 8-cm mass in the right anterior pelvic wall. Surgical resection of the mass revealed a high-grade, poorly differentiated leiomyosarcoma. Poland's syndrome is known to be associated with a high incidence of leukemia but this is the first description of its association with leiomyosarcoma. Although we cannot exclude the possibility of a chance association, it is reasonable to assume that, similar to other syndromes with multiple congenital anomalies, the association with an increased incidence of malignancy is an integral part of the underlying genetic abnormality.