Background: Malignant transformation of endometriosis is an infrequent complication of endometriosis. Extragonadal disease is uncommon.
Case: 55-year-old female presented with postmenopausal bleeding. Physical examination revealed a 2-cm polypoid lesion at the posterior vaginal apex, which was found to be a moderately differentiated invasive adenocarcinoma. Final pathology at the time of definitive surgery demonstrated a clear cell adenocarcinoma of the vagina arising in vaginal endometriosis.
Conclusion: Vaginal endometriosis may lead to the development of cancer. Malignancy arising in endometriotic foci is rare, but most commonly occurs in the ovary. We report a case of clear cell malignancy arising in vaginal endometriosis, adding to only seven cases previously reported. Risk factors include unopposed estrogen and obesity, but it may occur in the absence of either.