Uterine polyps with features overlapping with those of Müllerian adenosarcoma: a clinicopathologic analysis of 29 cases emphasizing their likely benign nature.

Müllerian adenosarcoma (MA) is a mixed Müllerian neoplasm composed of malignant stroma and benign epithelium. Endometrial and endocervical polyps are common entities in surgical pathology practice and most can be readily distinguished from MA; however, some have overlapping features, causing diagnostic confusion. In this study, we examined uterine polyps falling short of the diagnosis of MA quantitatively, qualitatively, or both. Our aims were to (1) characterize formally the morphologic features of atypical uterine polyps and (2) determine clinical outcome. Cases were evaluated for morphologic features of MA (phyllodes-like architecture, intraglandular polypoid projections, altered periglandular stroma, and stromal cytologic atypia), and the maximum number of mitoses per 10 high-power fields. The percentage involvement within a polyp by any atypical feature was estimated. The most common change was abnormal architecture, although periglandular stromal abnormalities and increased mitoses were also frequent findings. Stromal cytologic atypia was rare and when present was focal and mild. Histologic follow-up was performed in 24/29 (86%). Two patients had uterine polyps with unusual features similar to those noted on the initial biopsy. The remainder showed either polyp without unusual features or no residual polyp. Clinical follow-up information was available for 28/29 (97%). Twenty-seven of 28 were alive without evidence of disease, whereas 1 patient had died of pancreatic adenocarcinoma. We have shown that uterine polyps with features overlapping with those of MA have a benign clinical course, even with conservative management, as no cases showed progression or malignant transformation.