Bladder stromal tumor of uncertain malignant potential arising in ectopic prostatic tissue: Case report with MRI–pathology correlation

Stromal tumor of uncertain malignant potential (STUMP) is a rare mesenchymal neoplasm of the prostate with variable biological behavior and limited radiologic characterization. Most reported cases arise within the prostate gland. Ectopic prostatic tissue, defined as histologically confirmed prostate tissue outside the gland, is uncommon and most frequently identified in the bladder trigone, bladder neck, or urethra. We report the case of a 74 year-old man with a history of transurethral resection of the prostate who underwent prostate MRI due to elevated prostate-specific antigen levels. Imaging incidentally revealed a well-defined submucosal trigonal bladder nodule showing mild T2 hyperintensity, restricted diffusion, and avid early enhancement. Initial cystoscopic biopsy suggested ectopic prostatic tissue. Over a 4-year follow-up, the lesion demonstrated interval growth and the patient developed lower urinary tract symptoms and hematuria. Transurethral en bloc resection revealed a spindle cell stromal proliferation with mild atypia. Immunohistochemistry showed positivity for CD34, desmin, and progesterone receptors, consistent with STUMP arising in ectopic prostatic tissue. This case expands the radiologic spectrum of STUMP and highlights the importance of MRI and cystoscopic correlation in the evaluation of atypical bladder submucosal lesions.