A rare case of multifocal prostatic blue nevus: a case report

Introduction and importance: Prostatic blue nevus (PBN) is an exceptionally rare benign melanocytic lesion of the prostate, usually discovered incidentally. Case presentation: A 59-year-old Iranian male in otherwise good health presented to a urology clinic with an elevated PSA of 5.8 and obstructive symptoms. Digital rectal examination was normal. Trans-rectal ultrasound-guided biopsy revealed blue nevus in 4 out of 12 cores. Histology showed pigmented spindle cells in stroma confirmed by Fontana-Masson stain. Immunohistochemistry was positive for S100, HMB45, and Melan-A. No malignancy was seen. Clinical discussion: Blue nevus may be confused with malignant melanoma, especially in the absence of clinical suspicion. Immunohistochemistry plays a vital role in differentiation. The lesion has excellent prognosis and requires no follow-up beyond routine screening. Conclusion: We present a case of multifocal PBN identified during evaluation for lower urinary tract symptoms. Awareness of this entity is crucial to avoid misdiagnosis and unnecessary interventions.