Multimodal imaging features and symptom-directed management of primary prostatic granular cell tumor: a case report with 36-month follow-up

Background Granular cell tumor (GCT) is a rare neoplasm with characteristic abundant eosinophilic cytoplasmic granules and is most commonly associated with Schwannian differentiation. Primary prostatic GCT (GCT-P) is exceptionally rare, and published reports provide limited information on its imaging appearance and longitudinal clinical course. We describe the multimodal imaging findings, pathological confirmation, symptom-directed treatment, and 36-month follow-up of a patient with primary prostatic GCT. Case report A 46-year-old man presented with progressive dysuria and urinary retention. Ultrasound and magnetic resonance imaging (MRI) revealed diffuse enlargement of the prostate, with heterogeneous T2 hyperintensity, a T2-weighted “stripe sign” restricted diffusion, and a PI-RADS score of 5. Histopathological examination of transperineal prostate biopsy specimens showed tumor cells with abundant eosinophilic granular cytoplasm. Immunohistochemically, the tumor cells were strongly positive for CD68 and weakly positive for S-100, with additional supportive positivity for SOX10, NSE, and PAS-D. Expert pathological review at a higher-level hospital, together with the histopathological and immunohistochemical findings, supported the diagnosis of primary prostatic granular cell tumor. Because of severe bladder outlet obstruction, photoselective vaporization of the prostate (PVP) was performed as a symptom-directed debulking procedure. During 36 months of follow-up, the patient remained free of recurrent obstructive or residual urinary symptoms, with improved urinary function and no definite imaging progression. Conclusions Histopathological examination and immunohistochemistry were essential for diagnosis in this case. The T2-weighted “stripe sign” was observed on multiple sections and planes but remains a preliminary imaging observation requiring further validation. PVP provided substantial relief of bladder outlet obstruction in this patient as a symptom-directed debulking procedure. No definite imaging progression was observed during 36 months of follow-up, although these findings do not establish the long-term oncological efficacy of PVP for GCT-P.