意外發現的精阜腺癌：男性原發性尿道癌罕見病例報告

孫浩議¹、陳嘉宏¹、張彰琦^1,2、邱逸淳^2,3

¹臺北市立聯合醫院忠孝院區外科部泌尿科

²國立陽明交通大學醫學院

³臺北市立聯合醫院陽明院區外科部泌尿科

Unexpected Discovery of a Verumontanum Adenocarcinoma During TURP:
An Extremely Rare Case of Primary Male Urethral Cancer

Hao-Yi Sun ¹, Chia-Hung Chen ¹, Chang-Chi Chang ^1,2, Yi-Chun Chiu ^2,3

¹ Division of Urology, Department of Surgery, Zhongxiao Branch, Taipei City Hospital

² National Yang Ming Chiao Tung University, School of Medicine, Taipei, Taiwan

³ Division of Urology, Department of Surgery, Yangming Branch, Taipei City Hospital

Introduction:

Primary urethral carcinoma (PUC) is an exceptionally rare malignancy, accounting for less than 1% of genitourinary cancers, with an incidence of approximately 4.3 per million men. Among its histologic subtypes, adenocarcinoma arising from the male urethra is particularly uncommon, and involvement of the verumontanum—an anatomical region seldom harboring malignancy—is almost unheard of. Such lesions often evade early detection because their symptoms mimic benign prostatic obstruction or chronic inflammation, and serum prostate-specific antigen (PSA) levels typically remain within normal limits. This case describes an unexpected finding of primary urethral adenocarcinoma at the verumontanum discovered incidentally during laser transurethral resection of the prostate (TURP) for presumed benign prostatic hyperplasia (BPH). It highlights the diagnostic challenge of distinguishing malignant urethral lesions from benign conditions and underscores the importance of meticulous endoscopic inspection and comprehensive histopathologic evaluation, even when surgery is performed for nonmalignant indications.

Case presentation:

A 70-year-old man presented with progressive urinary frequency and weak stream for more than two years. His medical history included hypertension, hyperlipidemia, hemorrhoidectomy, and cholecystectomy. He had no family history of urologic malignancy and had a long-standing history of light smoking and occasional alcohol use. Despite medical management for lower urinary tract symptoms, his complaints persisted. Transrectal ultrasonography revealed a 64-gram prostate with an intact capsule and homogeneous echotexture. Uroflowmetry showed a decreased mean flow rate, and serum PSA was 3.3 ng/mL, consistent with benign prostatic enlargement. He was admitted for laser TURP. Intraoperatively, the urologist observed a tumor-like lesion at the left aspect of the verumontanum, accompanied by multiple erythematous patches over the bladder mucosa. The lesion was resected along with the prostatic adenoma tissue, and both specimens were submitted for histological evaluation. The postoperative course was uneventful, and he was discharged on the fourth day after surgery following successful voiding trial. Histopathological examination of the prostate tissue revealed benign prostatic hyperplasia without malignancy. In contrast, the verumontanum lesion displayed atypical glandular structures with prominent nucleoli and loss of basal cells, consistent with adenocarcinoma. Immunohistochemical staining was crucial in establishing the diagnosis: cytokeratin 7 and cytokeratin 20 were positive, while GATA3 and PSA were negative, and β-catenin showed nuclear reactivity, collectively favoring a diagnosis of primary urethral adenocarcinoma of enteric (colorectal-like) type rather than prostatic or bladder origin. Pelvic magnetic resonance imaging demonstrated no local invasion, and subsequent chest and abdominal computed tomography revealed no evidence of metastasis.

Conclusion:

This case illustrates an extremely rare primary urethral adenocarcinoma arising from the verumontanum, incidentally detected during laser TURP for BPH. Despite benign symptoms and normal PSA, malignancy can exist in unexpected sites. Thorough intraoperative inspection and histopathological analysis remain essential, as early recognition enables curative treatment and improves prognosis.