Positron emission tomography and leiomyomas: clinicopathologic analysis of 3 cases of PET scan-positive leiomyomas and literature review.

INTRODUCTION: Studies have suggested that PET scans can differentiate between leiomyomas and leiomyosarcomas. Our experience, however, shows that PET scan-positive smooth muscle tumors are not necessarily malignant. CASE REPORTS: Three patients with cancer underwent PET imaging. In all three, the most worrisome finding was a PET scan-positive uterine tumor. After surgical extirpation, all three uterine tumors were found to be benign smooth muscle neoplasms. DISCUSSION: To explore the potential reason these tumors were positive on PET imaging, we performed a detailed histopathologic and immunohistochemical study of all specimens. Pathologic evaluation revealed a leiomyoma, a cellular leiomyoma, and a stromomyoma. There was no association between an increased Ki67 (proliferative) index and positivity on PET imaging. Increased vascularity, however, appeared to be a feature common to the leiomyomas that were PET-positive.