Urachal carcinoma

The urachus is the remnant of an embryonic connection coursing from the dome of the fetal bladder to the umbilicus. After birth in normal children, it is limited to a thin cord-like structure. Rarely, a patent urachus is present at birth. More commonly, urachal diverticulum is present at the dome of the bladder (Fig. 6.15). Diagnosis can be made on VCU on lateral views. An urachal cyst is another pathogenic remnant of an urachus. It may be isolated or multiple. Infection can occur (Newman et al. 1986). Diagnosis is based on the association of clinical findings and ultrasound, which shows a superficial midline abscess-like structure. Urachal carcinoma does not occur in childhood (Thomas et al. 1986), but this possible complication in adulthood justifies surgical excision of urachal cysts in children. 

Thomas AJ, Pollack MS, Libshitz HI (1986) Urachal carcinoma evaluation with computed tomography. Urol Radiol 8 194-198... 

Adenocarcinomas of urinary bladder (urachal origin) are CDX2-I- but are also positive for thrombomodulin and CK7, whereas colorectal carcinomas are negative with thrombomodulin and CK7 and have nuclear beta-catenin expression. 

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