Polypoid endometriosis: a clinicopathologic analysis of 24 cases and a review of the literature.

We describe 24 cases of polypoid endometriosis, most of which were referred because of problems in differential diagnosis, particularly distinction from a low-grade müllerian neoplasm. The patients were 23 to 78 years (mean 52.5 years) of age. Seven patients were on unopposed estrogen, four on combined estrogen-progestin therapy, and one patient had a synchronous ovarian thecoma. The most common clinical presentations were a pelvic mass, vaginal polypoid masses, and large bowel obstruction. In some cases, the intraoperative findings suggested a neoplasm. Sites of involvement in order of frequency included colon, ovary, uterine serosa, cervical and/or vaginal mucosa, ureter, fallopian tube, omentum, bladder, paraurethral and paravaginal soft tissue, and retroperitoneum. Multiple sites were involved in seven cases. Five cases occurred within ovarian or extraovarian endometriotic cysts. The lesions ranged up to 14 cm in size and formed polypoid, pink, gray or tan, masses. On microscopic examination, the polypoid masses were composed of an admixture of endometriotic glands and stroma. A variety of glandular architectural patterns were observed, sometimes in combination, most commonly cystic and noncystic simple hyperplasia, but also simple or complex hyperplasia with atypia, disordered proliferative, and cystic atrophy. Various types of epithelial metaplasia (tubal, mucinous, squamous, papillary syncytial metaplasia) were common. Hemorrhage, fibrosis, prominent thick-walled blood vessels, hemosiderin-laden histiocytes, and decidual change were also present in some cases. Eighteen cases were associated with usual (nonpolypoid) endometriosis. In one case, polypoid endometriosis merged with a mucinous borderline tumor of endocervical-type. In all but two cases, polypoid endometriosis lacked periglandular stromal hypercellularity, stromal atypia, and intraglandular stromal papillae, helping distinguish it from adenosarcoma. Focal intraglandular stromal papillae were noted in two cases with focal mild periglandular stromal hypercellularity in one of them, but no stromal atypia was present in either case. Follow-up data in 17 patients indicated that 15 patients were alive without evidence of residual disease, 1 was alive with residual endometriosis, and 1 died of other causes. In conclusion, polypoid endometriosis is a rare manifestation of endometriosis that may be mistaken for a neoplasm on clinical, intraoperative, or pathologic assessment. Some cases may be attributable to exogenous hormones or hyperestrinism and, like conventional endometriosis, some may evolve into a premalignant or, rarely, a neoplastic lesion. The main lesion in the differential is a müllerian (mesodermal) adenosarcoma.