Transgelin, a Novel Marker of Smooth Muscle Differentiation, Effectively Distinguishes Endometrial Stromal Tumors from Uterine Smooth Muscle Tumors.

Differentiation between endometrial stromal sarcomas (ESSs) and smooth muscle tumors of the uterus can be challenging. Transgelin, a 22 kDa actin-binding protein has recently been shown to be a smooth muscle specific marker. The goal of this study was to determine whether transgelin could accurately distinguish ESSs from smooth muscle tumors. The expression of transgelin, CD10 and smooth muscle actin (SMA) in 13 ESSs (4 low grade, 6 undifferentiated and 3 metastatic), 9 smooth muscle tumors (1 leiomyoma and 8 leiomyosarcomas (LMSs) and 15 soft tissue LMSs was studied. The diagnostic performance of transgelin compared to the other smooth muscle markers was assessed. Transgelin was diffusely strongly positive in all myometria, leiomyoma, and uterine and soft tissue LMSs. In contrast, transgelin expression was totally absent in all endometria, primary and metastatic ESSs. SMA positivity was noticed in 4 of the 13 ESSs. CD10 was positive in most ESSs. Transgelin appears to be a specific marker of smooth muscle differentiation in the uterus with 100% sensitivity and specificity and may be useful for distinguishing LMS from ESS. It could be used as an additional marker useful for decision making, especially in those tumors with questionable histology.