LAUSR

Sir, We appreciate the comments of Reis and colleagues. They provide an updated review of literature and underscore the clinical implication of those findings. In regard to their enquiry about the histological features of urachal adenocarcinoma, seven of 11 cases of our series contained mucinous and cystic components resembling pancreatic or appendiceal mucinous neoplasm in the entire or a significant portion of the tumours. While using Sanger sequencing we were not able to identify hotspot mutations of GNAS, BRAF and NRAS in urachal adenocarcinoma, it is not surprising that more mutations can be detected by state-of-the-art technologies such as whole exome sequencing and pyrosequencing. Table 1 summarises the recently described mutations in urachal adenocarcinoma, mostly published after we submitted our manuscript. However, in contrast to the high frequency of GNAS mutation in pancreatic and appendiceal mucinous neoplasms, the overall incidence of GNAS mutation in urachal adenocarcinoma is low, indicating a different molecular oncogenesis, as Reis et al. have already commented. In addition, an ethnic factor should be considered. Our study has been the only Asian series concerning the mutations in urachal adenocarcinoma to date. A study conducted in our institution has demonstrated a significantly lower incidence of BRAF mutations in colorectal cancer than those reported in Western series. Given the possible linkage between urachal and enteric cancers, the frequency of BRAF mutation in urachal adenocarcinoma may be likewise low in this geographical region. We await further investigations to validate our observations.