陳祺方^{1, 2}、江百凱^{1, 2}

¹馬偕紀念醫院泌尿科, ²馬偕醫學院

Chi-Fang, Chen ^{1, 2}. Pai-Kai Chiang^{1, 2}

¹Department of Urology, Mackay Memorial Hospital, Taipei, Taiwan

²Department of Medicine, Mackay Medical College, Taipei, Taiwan

 

Prostatic stromal tumor of uncertain malignant potential (STUMP) is rare tumor of the specialized prostatic stroma origin that encompasses a broad spectrum of histologic patterns and clinical behavior. Herein, we aimed to present a case of STUMP at our institution which was initial diagnosis as huge prostate hyperplasia (196 gm.)

We reported a case of 79-year-old male patient had BPH with huge prostate volume (196gm) and presented with recurrent urinary tract infection and urine retention. The patient have taken doxaben since 5 years ago. Until Mar. 2018, he was admitted to our hospital under diagnosis of sepsis and urinary tract infection (UTI.) Difficulty voiding, decreased urine outpout were also complained. The digital rectal exam showed enlarged prostate and elastic consistency. The surface was smooth without perceptible mass lesion. His transrectal prostate echo showed 196 gm of prostate volume. The uroflowmetry showed low flow rate (Voiding volume: 165 ml, maximal flow rate (MFR): 5.5 ml/sec, average flow rate (AFR) 2.6 ml/sec ) with residual urine 26ml. PSA level in blood was 18 ng/mL. Transrectal ultrasonography (TRUS) of prostate biopsy was suggested; However, the patient refused.One year later, he came to our ER because of acute urine retention. Urine sedments analysis showed microscopic hematuria without pyuria (RBC/WBC: 165/6 cells/uL) Transurethral resection of prostate via thulium laser was indicated because of prostate related recurrent urine retention. During operation, the enucleated prostate adenoma was hard in consistency which is difficulty to resected by morcellator. The pathology result showed stromal tumor of uncertain malignant potential (STUMP) Ther resected prostate tissue was weighing 127 gm.

Microscopically, sections show prostatic tissue with proliferation of atypical spindle cells exhibiting hyperchromatic and pleomorphic nuclei within a myxoid stroma. Mitotic activity is rarely observed, and the MIB-1 labeling index is <10%. The atypical spindle cells are positive for progesterone receptor, focally positive for CD34 and desmin, while negative for SMA, S-100, CD117, DOG1, and STAT6. The histopathological and immunohistochemical features are consistent with stromal tumor of uncertain malignant potential (STUMP). Because of the prostate stromal tumor and the suspicious of prostatic sarcoma. Post. operation computer tomography (CT) scan was arranged for tumor extention and distant metastasis evaluation. (Fig2) There was no distant or extracapsular lesion

STUMPs are rare prostatic tumors of mesenchymal origin, that encompasses various of clinical behaviors.  Most cases presented with chronic lower urinary tract obstructive symptoms, abnormal digital rectal examination findings, and/or acute urine retention and elevated prostate specific antigen levels. Few cases revealed one intravesical protrusion solid or cytic tumor. Our case was infiltrated type tumor which mimicked huge prostate hyperplasia with urine retention.

The diagnosis of STUMP is based on histopathlogical report. Unlike glandular, papillary infolding cell arrangement as benign prostate hyperplasia, the atypical crowding spindle cell can be noted. It is important to distinguished STUMP from sarcoma series. STUMP had hypercellular stroma with scattered atypical cells, instead of prostate stroma sarcoma, but few or no mitotic figures are present.

Although most of these cases tend to be indolent, frequent local recurrences with malignant progression was also mentioned. Base on literature reviews, best strategy for STUMP is to close and longer follow-up with image survey or annual prostate biopsy.