Mesonephric-like adenocarcinoma as an unexpected histological result after fertility saving procedure for presumed adenomyosis: a case report

Introduction We report an unexpected case of mesonephric-like adenocarcinoma initially treated as a diffuse adenomyosis in a patient presenting with primary infertility. The aim of this report is to raise clinical awareness about the risk of a diagnostic pitfall where an unexpected malignancy can mimic diffuse adenomyosis. The patient’s main concerns and important clinical findings: A 41-year-old patient referred to a tertiary minimally invasive gynecological center in June 2023 for primary infertility, heavy menstrual bleeding, and a 5 x 6 cm myometrial mass diagnosed as diffuse adenomyosis on ultrasound scan. The primary diagnoses, interventions, and outcomes An open cytoreductive resection of adenomyosis with uterine cavity reconstruction was planned due to worsening abnormal uterine bleeding and two failed in vitro fertilization attempts. An unexpected Mesonephric-like adenocarcinoma with only small foci of healthy tissue was identified on histopathological examination, and immunohistochemical staining. Consequently, the patient had a total abdominal hysterectomy with bilateral salpingo-oophorectomy and systematic pelvic lymphadenectomy. This was followed by six cycles of paclitaxel and carboplatin plus pembrolizumab-based immunotherapy. Conclusions This case highlights the importance of thorough evaluation of all atypical myometrial lesions, including adenomyosis, where pre-conception surgical excision and histopathological evaluation are often deferred in most patients.