Pseudorosette-Like Proliferations of the Endometrium

The endometrium displays a wide spectrum of appearances in both neoplastic and non-neoplastic tissue. Unusual proliferations are not infrequently encountered and may lead to misinterpretation. In this study, we investigated pseudorosette-like proliferations (PLPs) found within the endometrial stroma which, to our knowledge, have not been previously reported. Nineteen endometrial samples with PLPs were identified over a period of 5 yr. Characteristics of the endometrium in which the PLPs were arising as well as patient information were recorded for each case. In addition, residual tissue from 10 of the cases was immunostained for cytokeratin, CD10, smooth muscle actin, S-100, and caldesmon to better characterize the lesions. In all cases the endometrium was in the proliferative phase and none of the patients reported the use of exogenous hormones. In 89% (17 of 19) of the cases, PLPs were present as a single focus; 2 cases showed multiple PLPs. Of the 10 immunostained cases, 90% (9 of 10) showed strong/diffuse staining for smooth muscle actin. Six cases showed negative or weak (1+) staining for CD10, whereas 3 showed moderate (2+) and 1 showed strong (3+) staining. In all cases the PLPs were negative for cytokeratin AE1/AE3, S-100, and caldesmon. These studies suggest that PLPs are benign proliferations with smooth muscle differentiation.