Fallopian tube nontuberculous mycobacterial infection caused by Mycobacterium abscessus mimicking fallopian tube carcinoma: A case report

Fallopian tube carcinoma is frequently detected at an advanced stage, and its imaging findings and tumor marker profiles are often indistinguishable from those of ovarian or peritoneal carcinoma. Nontuberculous mycobacteria (NTM) are environmental acid-fast bacilli with increasing clinical significance in both immunocompromised and immunocompetent individuals. Infection of gynecologic organs is extremely rare. This report describes a case of fallopian tube NTM infection caused by Mycobacterium abscessus that mimicked fallopian tube carcinoma. An 87-year-old woman underwent fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) during routine surveillance, which revealed focal FDG uptake in the right adnexal region. Serum CA125 was elevated, and magnetic resonance imaging demonstrated findings suspicious for fallopian tube carcinoma. Primary debulking surgery was performed. Intraoperative frozen-section examination of the right adnexa revealed necrotizing granulomas without evidence of malignancy, raising suspicion of mycobacterial infection. Fresh specimens were submitted for microbiological evaluation. Culture identified Mycobacterium abscessus , establishing the diagnosis of fallopian tube NTM infection. The patient was asymptomatic and had no abscess formation. Complete surgical resection was achieved, and no antimicrobial therapy was administered. The patient remained recurrence-free at 1-year follow-up. This case highlights the difficulty of differentiating infectious granulomatous disease from malignancy based on imaging findings alone. Intraoperative frozen-section examination played a crucial role in prompting microbiological investigation and establishing the correct diagnosis.