Leiomyomatous neoplasms of the lung: a clinical, histologic, and immunohistochemical study.

A series of 12 pulmonary lesions initially diagnosed as leiomyomatous in origin were reviewed. The original slides were analyzed for a series of histological features, the patients' charts were reviewed for clinical presentation and follow-up, and the usefulness of immunohistochemistry was assessed. Three groups were noted after analysis. Group 1, or benign lesions (three cases), all occurred in premenopausal female patients who remain alive and well. Group 2, or leiomyosarcomas (five cases), mostly occurred in older females, were thought to originate in the uterus, and resulted in death in four patients. In one of three cases of metastatic leiomyosarcoma, estrogen receptor was identified. Group 3 (4 cases) consisted of other diagnoses, including leiomyomatosis, fibrous histiocytoma, metastatic malignant melanoma, and metastatic synovial sarcoma. Immunohistochemistry was useful in separating nonsmooth muscle tumors and demonstrated muscle marker expression in all benign and most malignant smooth muscle lesions. Criteria are proposed for the diagnosis of pulmonary leiomyosarcoma, whether primary or secondary. In addition, if strict criteria are applied, the term "benign metastasizing leiomyoma" should be abandoned.