Endometriosis Involving the Bladder: A Contemporary Clinicopathologic Analysis of 88 Patients

Predominantly, case reports and small case series of endometriosis involving the bladder have been published. This study aimed to provide a contemporary clinicopathologic analysis of a large cohort of patients at a major academic center in the United States. A search was made through our urologic pathology database and expert consults of the senior author for patients with bladder endometriosis from 2006 to 2024. Eighty-eight patients were included. The mean age was 37 years (range: 18-80 years). Presenting symptoms included pelvic pain, abnormal uterine bleeding, dysmenorrhea, infertility, hydronephrosis, hematuria, bladder mass, pelvic mass, or an incidental finding during workup for other diseases. The bladder serosa was the most common site of involvement: 72 (82%) patients, followed by muscularis propria: 12 (14%) patients; perivesical adipose tissue: 11 (13%) patients, and submucosa: 1 (<1%) patient. Although none had malignant transformation, a subset presented as mimickers of bladder neoplasia. Fifty-six (62%) patients had involvement of other organs/sites, most commonly the ovary: 22 (25%); large intestine: 20 (23%); uterine serosa: 18 (20%); cul-de-sac: 15 (17%); broad ligament: 6 (7%), and other pelvis/abdominal cavity sites. CD10 was utilized in 9 (10%) patients. The mean duration of follow-up was 40 months (range: 1-208 months). All patients were alive at follow-up, with 30 (34%) having residual or recurrent endometriosis requiring additional treatment. This is one of the largest clinicopathologic studies to date of bladder endometriosis, and it may present as a mimicker of benign or malignant bladder neoplasia and frequently involves other sites.