A benign illusion: elevated CA 19-9 and bilateral xanthogranulomatous salpingitis hiding behind pelvic endometriosis

Xanthogranulomatous salpingitis (XGS) is a rare, benign, chronic inflammatory tubal condition that frequently mimics advanced malignancy, and its concurrent presentation with endometriosis is exceptionally rare. We present the case of an asymptomatic 44-year-old female who was found to have a complex tubo-ovarian mass and an elevated CA 19-9 during a routine solid organ donor evaluation. Suspecting malignancy, diagnostic laparoscopy was performed. Crucially, intraoperative frozen section analysis revealed benign pathology, prompting a fertility-sparing surgical approach involving left mass excision, right salpingectomy, and endometriosis resection. Final histopathology unexpectedly confirmed bilateral XGS with concurrent pelvic endometriosis. This case highlights that XGS can develop entirely silently alongside endometriosis, likely driven by chronic hemorrhage rather than bacterial infection. Intraoperative pathological evaluation is imperative to prevent the radical oncological overtreatment of complex, adherent adnexal masses.