Genetics and biological markers in urachal cancer
Urachal cancer (UraC) is a rare tumor entity that usually develops at the basis of the remnant embryologic urachus. Consisting of mostly adenocarcinomas, most patients present with secondary symptoms due to an advanced stage with urinary bladder infiltration. One third of patients are already metastasized at presentation rendering them unsuitable for curative surgical treatment. In order to improve staging, treatment and follow-up, adequate knowledge about the genetic origin and potential markers is necessary. This paper reviews the English literature until December 2015. Pathologists argue for and against metaplasia or remnant enteric cells as origin for the adenomatous tissue found in UraC. Mutations in KRAS, BRAF, GNAS and Her2 have been associated with UraC. Immunohistochemical (IHC) markers like CEA, 34βE12, Claudin-18 and RegIV are indicative for mucous producing UraC. So far, IHC markers fail as prognosticators when matched to clinical data. Little is known about serum markers for UraC. CEA, CA19-9, CA125 and CA724 are mentioned as being elevated in UraC by some reports. Regarding the literature for biological markers in UraC, knowledge is mostly derived from case reports or cohort studies mentioning markers or predictors. More genetic research is needed to show whether UraC stems from progenitor cells of the cloaca or is due to metaplasia of transitional cells. Few IHC markers have shown indicative potential for UraC. A useful panel for differential diagnostics and clinicopathologic prognostication needs to be developed. Serum markers show very little potential for neither diagnosis nor follow-up in UraC. Further research on larger cohorts is necessary.