Incidental Prostatic Stromal Tumor of Uncertain Malignant Potential (STUMP): Histopathological and Immunohistochemical Findings

Stromal prostate tumors are rare neoplastic proliferative lesions that have been classified into prostatic stromal tumor of uncertain malignant potential (STUMP) and prostatic stromal sarcoma (SS) based on these criteria: stromal cellularity, presence of mitotic figures, necrosis, and stromal overgrowth. A prostatic stromal tumor of uncertain malignant potential (STUMP) is a non-epithelial, mesenchymal spindle-cell tumor that can be classified as a specialized stromal tumor of the prostate. STUMPs have the capability to diffusely infiltrate the prostate gland and extend into adjacent tissues. Furthermore, they often recur and this is why they are considered as neoplastic entities. STUMPs usually tend to be not aggressive, but occasional cases have been reported with an extension into adjacent tissues. A few cases develop a sarcomatous dedifferentiation.

A 67-year-old male referred to the Department of Urology, Sapienza Rome University, with acute urinary retention (AUR) and bladder overdistention. Digital rectal examination (DRE) showed the presence of a severe prostatic hyperplasia and a transvesical prostatic adenomectomy (TVPA) was performed. The pathological evaluation performed at the Department of Pathology, Sapienza Rome University, revealed an incidental diagnosis of prostatic STUMP. The patient's follow-up is made every year with transrectal ultrasonography and nuclear magnetic resonance with spectroscopy, and every two years with a transperineal prostate biopsy to exclude a progression to a stromal sarcoma. After 5 years of follow-up the STUMP is still detectable but there is no sign of sarcoma. As a result of its relative rarity and lack of long-term follow-up, the prognosis of STUMP is unclear. Therapy varies from a wait-and-see approach to a radical retropubic prostatectomy.