Granulomatous Prostatitis after Bacille Calmette-Guérin Instillation Resembles Prostate Carcinoma: A Case Report

Abstract

Abstract Background: Bacille Calmette-Guérin (BCG) instillation is recommended in patients with non-muscle-invasive bladder cancer who have intermediate-risk and high-risk tumors. However, granulomatous prostatitis is a rare complication induced by BCG instillation, which can easily be misdiagnosed as prostate cancer. Here, we report a case of granulomatous prostatitis that resembled prostate cancer. Case presentation: A 64-year-old Chinese man who was diagnosed with non-muscle-invasive bladder cancer received BCG instillation. Three days later, he was diagnosed with urinary tract infection. He stopped BCG instillation and received anti-infective therapy. BCG instillation was restarted 14 months later. Three months after BCG restart, he presented with rising levels of total prostate-specific antigen (PSA) (9.14 ng/mL) and a decreasing ratio of free PSA/total PSA (0.09). Digital rectal examination revealed a moderately enlarged, non-painful prostate gland with normal density. In multiparametric prostate magnetic resonance imaging (MRI), axial T2-weighted images showed a 28 mm × 20 mm diffuse abnormality with a low signal in the right peripheral zone. On diffusion-weighted MRI with a high b-value, the lesion was seen as a markedly hyperintense focus, which was consistent with a lesion with a Prostate Imaging Reporting and Data System score of 5, with a hypointense signal on an apparent diffusion coefficient map image. Considering the possibility of prostate cancer, a prostate biopsy was conducted. Histopathology showed benign prostate tissue with typical features of granulomatous prostatitis. The nucleic acid test for tuberculosis was performed and the result was positive. The patient was finally diagnosed with BCG-induced granulomatous prostatitis. Thereafter, he stopped BCG instillation again and received anti-tuberculosis treatment. During a follow-up visit after 10 months, the patient presented with no evidence of tumor recurrence or symptoms of tuberculosis. Conclusion: Although histopathology is the only way to accurately differentiate between BCG-induced granulomatous prostatitis and prostate cancer, some clues such as temporarily elevated PSA levels and a high signal followed by a low-signal abnormality on high b-value diffusion-weighted MRI are important indicators of BCG-induced granulomatous prostatitis.