Polypoid uterine lesions mimicking endometrial stromal sarcoma

Two polypoid submucosal uterine lesions were examined histologically and im munohistochemically with monoclonal antibodies to desmin and alpha smooth m uscle actin. One case comprised a leiomyoma and the other a polypoid form o f adenomyosis. Both polyps had prolapsed through the external cervical os. The lesions had an ulcerated surface with focal areas of marked increased c ellularity and pronounced vascularity throughout, such that they mimicked a low grade endometrial stromal sarcoma infiltrating the myometrium. The cel lular areas showed diffuse positivity for desmin and alpha smooth muscle ac tin, confirming them to be of smooth muscle origin. The changes of marked h ypercellularity and pronounced vascularity within polypoid submucosal uteri ne lesions have not been emphasised in published reports up to now. Patholo gists should be aware of these morphological features in order to avoid mis diagnosis of such cases as endometrial stromal sarcomas. The changes descri bed here are likely to be secondary to trauma associated with a polypoid le sion prolapsing through the external cervical os.