Primary Synovial Sarcoma of the Prostate: A Case Report and Review of the Literature

Primary synovial sarcoma of the prostate is exceptionally rare. Its nonspecific presentation and often normal or low prostate-specific antigen (PSA) levels may delay diagnosis. A 49-year-old man presented with lower urinary tract symptoms and gross hematuria. Digital rectal examination revealed a markedly enlarged, firm, irregular prostate. The serum PSA level was 0.34 ng/mL. Pelvic magnetic resonance imaging showed a 9.4 × 7.4 × 6.5 cm heterogeneous prostatic mass with loss of the rectoprostatic fat plane, without definitive evidence of metastatic disease on staging. Transrectal ultrasound-guided biopsy demonstrated a monophasic spindle-cell neoplasm with immunohistochemical findings consistent with synovial sarcoma. Robot-assisted radical prostatectomy was converted to an open approach to facilitate resection. Tumor was identified in tissue from the rectoprostatic margin, while the overall margin status was indeterminate because of tumor fragmentation, raising concern for microscopic residual disease. The patient received adjuvant pelvic radiotherapy followed by doxorubicin and ifosfamide chemotherapy. At 20 months, he remained alive without radiologic evidence of recurrence or metastasis. Primary prostatic synovial sarcoma should be considered in younger to middle-aged patients with obstructive urinary symptoms, a large prostatic mass, and a normal or low PSA level. Diagnosis relies on histopathologic assessment, supported by immunohistochemistry and molecular testing whenever available. Management should be individualized through multidisciplinary discussion.