Vaginal villous or tubulovillous adenomas (TVA) are uncommon tumors histologically similar to their intestinal counterparts. After reviewing the literature, we report the eighth case of TVA, which presented as a polypoid tumor in the vagina, at suburethral level, in a 19-yr-old woman with Arnold-Chiari type II malformation and a myelomeningocele at birth. The tumor consisted of long villi lined by columnar cells with brush borders, pseudostratified nuclei, and foci of high-grade atypia. Immunohistochemistry was positive for cytokeratin 7, estrogen and progesterone receptors, CA19.9, p16, p53, and Ki-67 (53%), with a normal membranous pattern for β-catenin, but negative for cytokeratin 20, CDX2, carcinoembryonic antigen, chromogranin A, and synaptophysin. Neither human papillomavirus nor mutations in the K-RAS, BRAF, or LKB1/STK11 genes were detected. Although a rare neoplasm, awareness of this tumor is important as it must be distinguished from colonic adenocarcinoma or other malignant or benign conditions. The existence of 2 previously reported malignant cases merging with TVAs, and the presence of foci of high-grade dysplasia (p53-positive) in the present case, support TVA as a premalignant lesion.