The authors describe the clinicopathologic features of a group of endometrial polyps that exhibited large areas of infarction, to highlight the spectrum of morphologic alterations that may occur in this setting, including moderate cytologic atypia in a subset. Forty-one infarcted endometrial polyps, classified as such based on the presence therein of confluent zones of stromal necrosis and/or sharply demarcated zones of paucicellular to acellular stromal hyalinization, were assembled from multiple institutions. All were diagnosed in biopsies, polypectomies, or curettages. The morphologic profile of the epithelium associated with the infarcted zones was compared with those of a control group of 40 consecutive noninfarcted polyps. The patients with infarcted polyps ranged in age from 23 to 94 yr and were significantly older than the control group patients (mean ages, 60.8 vs. 49 yr respectively; P=0.02). The most common architectural alteration in infarcted polyps was a distinctive cellular tufting or pseudopapillary change, possibly representing an exuberant iteration of papillary syncytial change, which was seen in 39% of cases. Among the features that were significantly more prevalent in infarcted polyps than the control group were grade 2 pleomorphism (i.e., a 2-3-fold variation in nuclear size and/or shape) (37% vs. 2.5%, respectively; P=0.00029), cellular syncytia (44% vs. 15%; P=0.069), vesicular chromatin greater than background glands (56% vs. 7.5%; P <0.0001), hobnail cells (27% vs. 0%; P=0.0004), clear cells (12% vs. 0%; P=0.055), and eosinophilic cells (56% vs. 15%; P=0.000115). The 2 groups were not significantly different regarding mitotic index and a variety of other morphologic variables. Irrespective of morphology, epithelia within the infarcted zones at least focally showed a core immunophenotype (p53-wild type, p16-diffusely positive; low proliferative index) that was essentially identical to the phenotype displayed by foci of papillary syncytial metaplasia unassociated with polyps in a 10-case comparison group. None of the 34 patients with follow-up information has subsequently been diagnosed with a uterine neoplasm. In summary, infarcted endometrial polyps frequently display a spectrum of cytoarchitecturally atypical epithelial changes. These pseudoneoplastic alterations are most likely degenerative and/or metaplastic in nature.