Adenocarcinoma arising in a rectovaginal fistula in Crohn disease

Adenocarcinomas occurring in the vagina are rare. Their correct classification may be very challenging to both the gynecologist and the pathologist, but it is essential for appropriate therapy. Although most adenocarcinomas in the vagina arise from other sites in the female genital tract, a significant minority reflects metastasis from a colorectal site. We report a very unusual occurrence of an adenocarcinoma that presented as a mass in the vagina protruding through the introitus. It arose in a rectovaginal fistula consequent to chronic Crohn disease, but it did not extend to involve the colonic mucosa. Neither the initial clinical examination nor the pathologic examination suggested the correct diagnosis. We report this case to remind the gynecologists of the potential complications of Crohn disease, and to highlight for the pathologists the difficulty that is often encountered in the correct identification of the source of carcinomas that are found in the vagina.