A Rare Case of a Urachal Mucinous Cystic Tumour of Low Malignant Potential.
During early embryonic development, the allantois forms as a vestigial membrane which originates from the cloaca and passes into the connecting yolk sac stalk. Between the 5th and 7th week gestation, the lower part of the allantois forms the bladder, and the intra-abdominal portion of the allantois evolves into the urachus
which drains into the bladder. From the 32nd week gestation, descent of the bladder towards the pelvis stretches the urachus, causing its lumen to obliterate and transform into the median umbilical ligament. If this obliterative process is incomplete, this can lead to a persistently
patent urachal remnant.
This occurs in approximately 32% of the adult population and is most commonly located within the bladder dome, and may extend to the umbilicus. A patent urachus consists of an outer muscular layer and a lumen which is usually lined by urothelium with occasional foci of glandular metaplasia. The exact course of a patent urachal remnant remains unknown; however, its persistence has shown to rarely undergo malignant transformation, accounting for 0.07-0.34% of all bladder carcinomas.
Neoplasms of the urachus are predominantly glandular, and most are high grade invasive adenocarcinomas, representing 20-39% of bladder
adenocarcinomas. In addition, there is a small subgroup of urachal glandular tumours that are cystic and have a
striking resemblance to mucinous epithelial tumours of the ovary. Whilst these mucinous cystic tumours of the urachus have only been studied in case reports and small case series
its classification has been proposed by Amin et al and later modified in the
WHO 2016 Classification of Tumours of the Urinary system and
Male Genital Organs.
Cancer Stud Mol Med Open J. 2018; 4(1): 5-9. doi: 10.17140/CSMMOJ-4-122