Polypoid endometriosis of the bladder during pregnancy mimicking urachal carcinoma.

We report a case of polypoid bladder endometriosis in pregnancy. Diagnostic workup showed a vesicouterine well-vascularized polypoid mass, suspicious for malignancy. During pregnancy, the mass was surgically resected with safe oncological margins. Pathological examination of the resected specimen revealed pseudotumoral polypoid endometriosis of the bladder. We illustrate diagnostic pitfalls in the differentiation between bladder endometriosis during pregnancy and malignancy. As a result of pregnancy-related decidualization of vesical endometriosis, differentiation between this rare occurrence and malignant transformation is challenging.