Solitary fibrous tumor of the prostate

Solitary Fibrous Tumor of the Prostate Treated with Frozen-Section Supported Robot-Assisted Nerve-Sparing Radical Prostatectomy

INTRODUCTION

Solitary fibrous tumors (SFTs) of the prostate are extremely rare. We report on a 60-year-old man who was diagnosed with prostatic SFT through transurethral resection (TUR) of the prostate, and we provide a narrative literature review to put the case into perspective. We looked into multiple databases for articles published before June 2022.

CASE REPORT

A 60-year-old man without comorbidities presented with acute urinary retention and significant macrohematuria. Due to recurrent bladder tamponades and relevant blood loss despite irrigation, an emergency endoscopic transurethral evaluation was initiated. Intraoperatively, diffuse venous hemorrhage from prostatic vessels around the bladder neck was detected, as well as significant hemorrhage from a grossly enlarged and tumor-suspicious prostate middle lobe. Within the framework of extensive bipolar coagulation, parts of the suspicious middle lobe were removed via TUR. The final histopathology report showed incompletely resected SFT of the prostate. Due to the extremely rare SFT diagnosis, the case was discussed in an interdisciplinary tumor board and further diagnostic workup, including thoracoabdominal computed tomography and magnetic resonance imaging of the pelvis, was performed, which revealed no secondary tumors or signs of metastasis. According to the tumor board recommendation, robot-assisted radical prostatectomy (RARP) with bilateral nerve sparing was performed, supported by intraoperative frozen section. The final histopathology confirmed the SFT that had developed from the transition zone. The SFT was resected with negative frozen section result and negative surgical margins (R0). No intra- and perioperative complications occurred, and in the short-term follow-up, the patient presented in excellent general status with full continence. From 1997 to June 2022, we identified a total of 12 publications reporting on treatment for prostatic SFT (11 case reports and 2 patient series), with none performing bilateral nerve sparing, frozen section, or robot-assisted radical prostatectomy. No common survival endpoints were accessible.

CONCLUSION

This case demonstrates the exceedingly rare case of SFT of the prostate, which has been described in the literature in only 23 men worldwide. Here, we were the first to demonstrate the feasibility of bilateral nerve-sparing RARP supported by frozen section. A systematic review was not possible due to the lack of common endpoints.

Solitary fibrous tumors of the prostate: A case report

Increasing numbers of extrapleural solitary fibrous tumours (SFTs), including the prostate SFT, have been reported over the last 10-years. Prostate SFT is relatively uncommon, with <20 cases reported in the literature worldwide. In the present study, a prostate SFT case, which was initially misdiagnosed as benign prostatic hyperplasia, is presented. The patient was subjected to three surgeries (cystoscopy and per urethra lithocystotomy, transurethral resection of the prostate and nerve-sparing retropubic radical prostatectomy) prior to SFT diagnosis. It was demonstrated that histopathological and immunohistochemical factors (positive staining for CD34 and B cell lyphoma-2 expression) were of significant diagnostic value. Thus, nerve-sparing retropubic radical prostatectomy for total resection may be the best therapeutic strategy to treat prostate SFT, allowing the preservation of sexual function and reducing the risk of locoregional recurrence.

Complex cellular composition of solitary fibrous tumor of the prostate

Solitary fibrous tumors (SFTs) of the prostate are a rare type of spindle cell neoplasm that can demonstrate either a benign or malignant phenotype. SFTs represent a clinical challenge along with other spindle cell lesions of the prostate in terms of both diagnosis and treatment. The present study shows, for the first time, that SFTs of the prostate and other organs can comprise a mixed population of fibroblast, myofibroblast, and smooth muscle cell types. The highly proliferative component demonstrated a fibroblastic phenotype that readily underwent myofibroblast differentiation on exposure to profibrotic stimuli. Consistent with other recent studies, the prostatic SFTs demonstrated NAB2-STAT6 gene fusions that were also present in the fibroblast, myofibroblast, and smooth muscle cell types of the SFT. The results of these studies suggest that benign and malignant prostatic tumors of mesenchymal origin may be distinguished at the molecular and cellular levels, and that delineation of such defining characteristics may help elucidate the etiology and prognosis of such tumors.

Non-epithelial neoplasms of the prostate

Non-epithelial prostatic neoplasms are infrequent and cover a broad array of entities that include both benign and highly aggressive tumours. Because they are very infrequent, there is often limited understanding of them, and the recognition of these entities, when encountered, may pose a diagnostic challenge, owing to histological overlap between them or their rarity. Most lesions in this category are mesenchymal in origin, such as prostatic stromal tumours arising from specialized prostatic stroma, smooth muscle tumours, both benign and malignant, and solitary fibrous tumours. Less commonly occurring tumours include neural, germ cell and melanocytic tumours that may be derived from cells not normally present in the prostate. Some tumours have well-established extraprostatic counterparts and, when encountered, are more commonly extraprostatic/secondary in origin; these include gastrointestinal stromal tumours and most haematopoietic tumours. The majority of tumours are characterized by a spindle cell pattern with significant overlap in morphological features. In this setting, appropriate use of immunohistochemistry and molecular studies are often necessary for accurate diagnosis, prognosis, or prediction for therapy. This review addresses and updates the clinicopathological features of the entire spectrum of non-epithelial tumours with an approach to the histological diagnosis.

Solitary fibrous tumor of the prostate: case report and review of the literature

Solitary fibrous tumor (SFT), usually described in the pleura, is exceedingly rare in the prostate. We report a 60-year-old man with prostatic SFT revealed by obstructive urinary symptoms, and detected by ultrasonography. Computed tomography (CT) and magnetic resonance imaging suggested a prostatic origin. CT-guided tumor biopsy diagnosed a SFT. A cystoprostatectomy was performed. Pathologic examination showed a 15-cm tumor arising from the prostate and showing histological criteria suggestive of aggressiveness. The surgical resection margins were tumor-free. The patient was then regularly monitored and is still alive in complete remission, 28 months after surgery. In conclusion, we report a new exceptional case of prostatic SFT. We review the literature and discuss the challenging issues of misdiagnosis, prognosis and treatment.

Mesenchymal Tumors of the Prostate

Prostatic mesenchymal tumors encompass various benign and malignant neoplasms that may derived from the intrinsic prostatic stroma or from associated elements including muscle, connective tissue, blood vessels, and neural structures. The differential diagnosis of these tumors is broad and encompasses prostatic epithelial processes that demonstrate prominent spindle cell morphology, as well as mesenchymal tumors that secondarily involve the prostate. Careful morphologic examination, clinical history, and judicious use of a limited panel of immunohistochemical markers and molecular tests aid in the proper diagnosis of these lesions. This article provides a structured guide for the analysis and diagnosis of both benign and malignant prostatic mesenchymal lesions and highlights key features that distinguish these entities within the differential diagnosis of prostatic spindle cell lesions.

Solitary Fibrous Tumor on Needle Biopsy and Transurethral Resection of the Prostate

One of the least commonly encountered spindle cell tumors seen on prostatic needle biopsy or transurethral resection (TUR) of the prostate is solitary fibrous tumor (SFT). We studied 13 cases of SFTs identified on either prostate needle biopsy (n=9) or TUR of the prostate (n=4). Mean patient age at diagnosis was 63 years (range: 46 to 75 y; median: 65 y). Twelve men presented with urinary tract symptoms and 1 patient was biopsied during work-up of bone metastases. Ten cases were SFTs originating in the prostate, 2 cases arose between the prostate and rectum extending into the prostate (n=2), and 1 case was a pelvic mass without infiltration of the prostate. In 9 cases, a complete tumor resection was attempted by cystoprostatectomy (n=2), radical prostatectomy (n=4), pelvic exenteration (n=2), or pelvic tumor resection (n=1). Enucleation (n=1) and TUR (n=1) were performed in 2 other cases. Tumor sizes ranged from 8.5 to 15 cm in 7 radically resected cases. Mitotic rates were 3 to 5 per 10 high power fields in 5 cases, with the remaining cases having either rare (n=4) or no mitoses (n=4). Seven cases demonstrated areas of necrosis. Based on a combination of increased cellularity, mitotic activity, necrosis, nuclear pleomorphism, and infiltrativeness, 4 prostatic SFTs were malignant, 4 were benign, and 2 were borderline. Of the 3 non-prostatic SFTs, 1 was malignant and 2 were borderline. All tumors but 1 were immunoreactive for CD34 (n=12). Material for additional immunohistochemistry was available for the majority of cases with positive stains for Bcl-2 (11/11), CD99 (7/10), beta-catenin (5/10), and c-kit (0/11). Three SFTs demonstrated >or=10% p53 immunoreactivity including 1 tumor with 50% positivity; and 3 cases had Ki-67 rates of >or=20%. Although all SFTs were initially clinically considered to be of prostatic origin, some of the cases arose in the pelvis with secondary involvement of the prostate. Approximately 50% of prostatic SFTs were malignant. Even in the prostatic and nonprostatic SFTs with no overt malignant features, sometimes it was necessary to remove the prostate and in some instances the adjacent organs because of the large size of the tumors. SFTs must be differentiated from other spindle cell neoplasms of the prostate especially from gastrointestinal stromal tumors that may arise from the rectal wall with invasion of the prostate or from the region between the rectum and the prostate.

Spindle cell lesions of the adult prostate

Prostatic spindle cell lesions are diagnostically challenging and encompass a broad array of benign and malignant processes. A subset of these lesions arises only within the prostate and generally represents entities that originate from the prostate epithelium or stroma, such as sclerosing adenosis, sarcomatoid carcinoma, stromal tumors of uncertain malignant potential (STUMP), and stromal sarcoma. Another subset of spindle cell tumors that involve the prostate are also found at other sites and include solitary fibrous tumor, leiomyosarcoma, and neural lesions among others. Finally, tumors may secondarily involve the prostate yet present as primary prostatic processes, as is evident with several cases of gastrointestinal stromal tumors (GIST). The utility of ancillary studies, including immunohistochemistry, is often limited and the main criteria for diagnosis are the morphologic findings by routine H&E stain. This review addresses the various entities that may present as spindle cell tumors within the adult prostate and discusses the functional aspects of the differential diagnosis of these lesions.

Solitary fibrous tumor of the thyroid gland: report of two cases and review of the literature

Presented herein are the first two Japanese cases of solitary fibrous tumor (SFT) of the thyroid gland. The patients were 64- and 41-year-old men, who underwent hemithyroidectomy for thyroid tumors. Histopathologically, the tumors were well circumscribed, and were composed of spindle cells, collagen bundles and entrapped thyroid follicles. Spindle cells and collagen bundles were mostly in a patternless arrangement with an admixture of hypo- and hypercellular areas. Proliferating spindle cells were bland, slender, and occasionally wavy without any atypia and increased mitotic figures. Immunohistochemically, they were strongly positive for CD34, CD99, and bcl-2, but negative for epithelial membrane antigen, keratin, thyroglobulin, calcitonin, thyroid transcription factor-1, alpha-smooth muscle actin, desmin, S-100 protein and CD117. Based on these findings, the two patients were diagnosed as having thyroid SFT. Neither local recurrence nor metastasis has been observed in 5 years in patient 1 or in 4 years in patient 2. Thyroid SFT is extremely rare, and only 20 cases have been reported in the English-language literature including hemangiopericytoma. Although recurrence or metastasis has not been described in any reported cases, the clinical behavior of SFT is still undetermined, therefore long-term follow up seems necessary at present.

Imaging findings of solitary fibrous tumor of the prostate: a case report

The imaging findings of a solitary fibrous tumor of the prostate are presented. A 35-year-old male presented with urinary retention and was found on transrectal ultrasonography to have a hypoechoic tumor of the prostate, measuring 5.5 cm in size. Magnetic resonance imaging on, the tumor showed low signal intensity on T1-weighted images and heterogeneous mixed signal intensity on T2-weighted images. Gadolinium-enhanced dynamic study showed gradual enhancement from the periphery to the center, and the enhancement is sustained. On immunohistochemistry, the spindle cells of the tumor showed positive staining for CD34 and bcl-2. Although the tumor was labeled as a low-grade malignancy on account of a low mitotic index (MIB-1 index) of about 5%, the patient developed local recurrence of the tumor with bladder wall invasion 12 months later.