The oncogenic phosphatidylinositol 3-kinase-AKT-mammlian target of rapamycin pathway (PI3K-AKT-mTOR) pathway is known to be activated in uterine smooth muscle tumors, and Stathmin 1 (STMN1) expression has been identified as a marker of PI3K-AKT-mTOR pathway activation. We hypothesized that STMN1 may have some diagnostic utility and explored how well STMN1 expression correlated with histologic classifications of uterine smooth muscle tumors into benign and malignant groupings. 84 smooth muscle tumors were assessed for STMN1 expression by immunohistochemistry. These included spindle cell leiomyosarcoma (n=32), conventional spindle cell leiomyomas (n=30), atypical (symplastic) leiomyoma (n=5), cellular leiomyoma (n=7), smooth muscle tumor of uncertain malignant potential (n=4), mitotically active leiomyomas (n=2), benign metastasizing leiomyoma (n=3), and cotyledonoid dissecting leiomyoma (n=1). All spindle cell leiomyosarcomas were positive (32/32 positive; 100%) as compared with conventional leiomyomata (11/30; 37%) (
