Clear Cell Adenocarcinoma of the Colon Arising in the Background of Endometriosis: A Case Report and Diagnostic Approach

Clear cell adenocarcinoma of the colon is rare, with only a handful of cases reported in the literature. Some of these cases are attributed to endometriotic involvement of the colonic wall; however, a presence of the clear cell adenocarcinoma and endometriotic glands with dysplastic clear cell changes in the colonic wall has not been compellingly demonstrated. We describe a case of clear cell adenocarcinoma of rectosigmoid in a 41-year-old woman, where we have been able to document endometriotic glands with dysplastic clear cell transformation in the background. The presence of the endometriotic glands and the endometrial stroma is confirmed with immunohistochemical stains. The diagnostic approach and immuhistochemical characteristics of these neoplasms are discussed along with difficulties in staging of these tumors.