A rare case of primary clear-cell adenocarcinoma of the bladder arising from bladder endometriosis

Endometriosis is a common benign gynaecological condition affect-ing 5–15% of women in their reproductive age and only 3–5% of post-menopausal women, in which endometrial tissue grows outside uterine cavity, leading to pelvic pain and infertility (Vignali et al. 2002). Even if endometriosis is a benign condition, it can spread to other organs by invading and disrupting their tissues, sharing these characteristics with invasive cancers. It is well known that ovarian cancer, especially endometrioid and clear cell types, can be the result of a malignant transformation of foci of endometriosis (Bacci et al. 2009), but even if extra-gonadic endometriosis malignant transfor-mation was considered an exceptional event, recent studies suggested that it can also be associated with other kinds of cancer (Ness 2003; Olson et al. 2002; Scully et al. 1966).Primary clear-cell bladder adenocarcinoma is a very rare tumour, affecting mostly women; it can be associated with bladder endometri-osis suggesting a mullerian origin of this rare cancer (Lu et al. 2012).