p53 mutation in adenocarcinoma arising in retrorectal cyst hamartoma (tailgut cyst) - Report of 2 cases - An immunohistochemistry/immunoperoxidase study

Retrorectal cyst hamartoma (RCH) is a rare benign cystic lesion located in the retrorectal space. Malignancy arising in such lesions is very uncommon. In this study, 2 cases of mucinous adenocarcinoma arising in RCH are prese nted. in one case, dysplastic epithelium lined the cyst wall, surrounding t he area of carcinoma and suggesting a dysplasiacarcinoma progression in RCH . Adenocarcinoma and the dysplastic epithelium were strongly positive for p 53 and Ki-67 and showed negative staining for p21 by immunohistochemistry. These findings are suggestive of a mutation in the p53 gene in the adenocar cinoma and in dysplastic epithelium lining the cysts, similar to the dyspla sia-carcinoma sequence described for the development of colonic adenocarcin oma.