A Rare Case of a Solitary Fibrous Tumor of the Prostate: A Case Report.

Spindle cell lesions of the prostate are rare and diagnostically challenging, encompassing entities such as stromal tumors of uncertain malignant potential (STUMP), sarcomas, sarcomatoid carcinoma, and mesenchymal tumors, including solitary fibrous tumor (SFT), which is exceedingly uncommon in the prostate. A 64-year-old male presented with progressively worsening lower urinary tract symptoms over several months, culminating in an episode of acute urinary retention. The patient underwent transurethral resection of the prostate (TURP) for symptomatic relief and tissue diagnosis. TURP was performed due to persistent obstructive urinary symptoms and acute urinary retention. Histopathological examination revealed a cellular spindle cell neoplasm arranged in haphazard sheets and fascicles, associated with intervening staghorn-shaped vasculature and a hyalinized stroma. The tumor exhibited increased mitotic activity and an expansile, non-infiltrative growth pattern. Immunohistochemical analysis demonstrated strong nuclear STAT6 expression and diffuse CD34 positivity, while epithelial, myoid/myofibroblastic, neural, and synovial sarcoma markers were negative, confirming the diagnosis of SFT. Although the diagnosis was established based on morphology and immunoprofile, adverse histologic features, such as increased mitotic activity and high cellularity, suggest potential malignant behavior, warranting close clinical follow-up. This case underscores the importance of thorough histopathological and immunohistochemical evaluation in distinguishing SFT from other spindle cell lesions of the prostate, particularly given its extreme rarity and potential implications for patient management and follow-up.