前列腺切片未見惡性但骨轉移證實前列腺癌：一病例報告

江冠億¹、李淑文¹、鄭企峰²、薛又仁³、賴昱維¹、邱文祥⁴

¹臺北市立聯合醫院仁愛院區 外科部 泌尿科；²臺北市立聯合醫院仁愛院區 內科部 血液腫瘤科；³臺北市立聯合醫院和平婦幼院區 外科部 泌尿科；⁴新光醫療財團法人新光吳火獅紀念醫院 外科部 泌尿科

Metastatic Prostate Cancer Confirmed by Bone Biopsy Following a Negative Prostate Biopsy: A Diagnostic Challenge

Kuan-I Chiang¹, Shu-Wen Li¹, Chi-Feng Cheng², Thomas Y. Hsueh³, Yu-Wei Lai¹, Allen W. Chiu⁴

¹Division of Urology, Department of Surgery, Taipei City Hospital Renai Branch, Taipei, Taiwan; ²Division of Hematology and Oncology, Department of Internal Medicine, Taipei City Hospital Renai Branch, Taipei, Taiwan; ³Division of Urology, Department of Surgery, Taipei City Hospital Heping Fuyou Branch, Taipei, Taiwan; ⁴Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan

Introduction:

Prostate cancer is one of the most common malignancies among men worldwide. Serum prostate-specific antigen (PSA) and transrectal ultrasound-guided prostate biopsy (TRUS biopsy) are widely used for screening and diagnosis. However, the false-negative rate of systematic biopsy has been reported to be 21–28%, often due to sampling error or tumors located in difficult-to-sample regions such as the anterior prostate. In rare cases, metastatic lesions may provide the first pathological confirmation when prostate biopsy is negative.

Case Presentation:

A 72-year-old man with benign prostatic hyperplasia, hypertension, diabetes mellitus, and dyslipidemia presented with bilateral hip pain for three months. He also had long-standing lower urinary tract symptoms and intermittent hematuria. Imaging at another hospital revealed multiple osteoblastic spinal lesions and pulmonary nodules, raising strong suspicious for metastasis. PSA level was markedly elevated (81.8 ng/mL), and transrectal ultrasound demonstrated a markedly enlarged prostate (137 g). The patient underwent cystolitholapaxy, GreenLight photoselective vaporization of prostate and TRUS-guided prostate biopsy (12 cores), which however, revealed no malignancy. Due to persistent suspicion, further evaluation was performed. Bone scan demonstrated multiple skeletal metastases. CT-guided biopsy of the right ilium revealed metastatic carcinoma forming atypical glands. Immunohistochemistry showed PSA and NKX3.1 positivity, confirming a diagnosis of metastatic carcinoma of prostate origin.

Discussion:

TRUS-guided biopsy remains the standard diagnostic method, but false-negative results occur in up to 28% of cases. Large prostate volume significantly decreases biopsy sensitivity, particularly when tumors are located in the anterior region. In this case, the prostate measured 137 g, which likely contributed to the negative biopsy result. When clinical suspicion remains high, additional diagnostic strategies such as multiparametric MRI, repeat biopsy, or biopsy of metastatic lesions should be considered. Immunohistochemical markers including PSA and NKX3.1 are highly useful in confirming prostatic origin in metastatic disease.

Conclusion:

A negative prostate biopsy does not exclude prostate cancer in patients with markedly elevated PSA and radiologic evidence of metastasis. Biopsy of metastatic lesions may be crucial for establishing the diagnosis and initiating appropriate treatment.