Endometrioid carcinoma of the fallopian tube misdiagnosed as an infected endometrioma: A case report

INTRODUCTION: Fallopian tube cancer is a rare tumor, representing between 0.3 and 1.8 % of all malignant tumors in the gynecological sphere. Due to the proximity of the uterus and ovary, the diagnosis of primary fallopian tube cancer is very difficult to establish and relies on very strict criteria. The endometrioid form is exceptional and of controversial etiopathogenesis. Only a few cases have been previously reported. Diagnosis most often occurs incidentally during histological examination. This case presents a distinctive aspect with the rare occurrence of endometrioid-type fallopian tube cancer, notably associated with endometriosis, and initially misdiagnosed as an infected endometrioma. It underscores the diagnostic complexities encountered in identifying primary fallopian tube cancer. CASE REPORT: We present the case of a 49-year-old patient, followed for chronic pelvic pain associated with menorrhagia. Imaging revealed a myomatous and adenomyotic uterus, a right ovarian endometrioma, and a left multicystic ovarian formation with thick walls, measuring 135 mm, requiring histological verification. She underwent an exploratory laparotomy. During the procedure, extensive retro- and supravaginal adhesive tissue involving the uterus, both adnexa, and the digestive tract was found. Careful adhesiolysis was performed. The left adnexa harbored a formation suggestive of an infected endometrioma. A total hysterectomy with bilateral adnexectomy and peritoneal washing was performed. The postoperative course was uneventful. Histopathological examination revealed an endometrioid carcinoma of the left fallopian tube, classified as pT1a according to FIGO guidelines. DISCUSSION: Tubal cancer is a rare cancer of unknown etiology, underestimated, and sometimes confused with ovarian pathology. Preoperative diagnosis is difficult because the clinical presentation is polymorphic and imaging is nonspecific. The endometrioid form is exceptional and of controversial etiopathogenesis. Treatment mirrors that of malignant epithelial ovarian tumors, with prognosis depending on FIGO stage and histological type. CONCLUSION: Due to its unpredictable nature, fallopian tube cancer should not be overlooked as a differential diagnosis for any adnexal mass.