Concurrent prostatic stromal tumor of uncertain malignant potential and prostatic adenocarcinoma: A case report exhibiting advantages of a Multidisciplinary Team

Abstract

Prostatic stromal tumor of uncertain malignant potential is a rare tumor of the prostatic gland. We present a case, in which the tumor was found alongside prostatic adenocarcinoma, that was evaluated in a Multidisciplinary Team setting, consisting of urologists, nuclear medicine specialists, radiologists and pathologists, and through surgery was successfully treated. The case report suggests that this multidisciplinary approach might improve clinical decision making in cases of limited evidence based recommendations.

1. Introduction

This is a case of how a Multidisciplinary Team managed a giant cystic tumor in the prostate. The tumor turned out to represent concurrent presence of the rare prostatic stromal tumor of uncertain malignant potential (pSTUMP)¹ and regular prostatic adenocarcinoma. Along with these findings, the possibility of another rare cystic tumor of the prostate was considered closely: Giant multilocular prostatic cystadenoma (GMPC) Both rare tumors has a malignant counterpart, respectively: prostatic stromal sarcoma (PSS)² and multilocular prostatic cystadenocarcinoma,³ both equally rare to pSTUMP and GMPC.

Concurrent pSTUMP and regular prostatic adenocarcinoma has previously been described.4, 5, 6

2. Case presentation

A 50-year-old male, presenting with lower urinary tract symptoms and elevated levels of prostate-specific antigen (PSA) at 47 ng/mL was referred to the department of urology at Gødstrup Hospital. Magnetic Resonance Imaging (MRI)-scan visualized a giant prostatic cystic process – measuring 9.7 x 16.7 × 11.2 cm, displacing both the rectum and urinary bladder, with no suspicion of malignancy. Giant multilocular prostatic cystadenoma (GMPC) was proposed as the most probable diagnosis – a very rare and benign urological condition⁷ (Fig. 1).

Fig. 1.

MRI images.

Together A and B illustrate a large, cystic process, filling the entirety of the small pelvis. The rectum is displaced to the right-side and the urinary bladder cranially.

The cystic parts have varying signals, indicating that they contain varying amounts of protein. Centrally the tissue seems more solid.

The dark belt in the top of picture B, is a saturation belt, used to reduce noise created by motility of the intestines.

A: Axial T2-weighted Turbo spin echo sequence with Deep Resolve Boost (slice thickness of 4 mm and spacing 10 %).

B: Axial T2-weighted Turbo spin echo sequence with Deep Resolve Boost (slice thickness of 3 mm and spacing 0 %).

The patient's case was discussed on the weekly prostate Multidisciplinary Team (MDT)-conference with specialists in Urology, Radiology, Oncology and Nuclear Medicine, from two collaborating hospitals.

Based on conference decision, the patient underwent additional diagnostic imaging, both ¹⁸F-Prostate-Specific Membrane Antigen – Positron Emission Tomography/Computed Tomography (¹⁸F-PSMA-PET/CT), to detect potential malignancy and metastases, and CT-urography to identify the ureters and plan surgical intervention.

¹⁸F-PSMA-PET/CT showed solid PSMA-avid areas on both sides of the prostatic cystic tumor (Fig. 2), that were suspicious of malignancy. The CT-urography identified normal ureters without hydronephrosis, hydroureter, nor delayed contrast excretion.

Fig. 2.

¹⁸F-PSMA-PET/CT images.

A: Coronal images with arrows highlighting the left side area with maximum PSMA-uptake. Top: Fusion of PSMA-PET/CT-PET and CT. Middle: PSMA-PET/CT. Bottom: CT

B: Axial images, arrows highlighting both right- and left side areas with increased PSMA-uptake. Top: Fusion of PSMA-PET/CT-PET and CT. Middle: PSMA-PET/CT. Bottom: CT

C: Maximum Intensity Projection (MIP).

At the following MDT-conference, the added suspicion of malignancy increased the importance of knowing whether the cystic process contained mucin as it would result in increased complication rates due to the risk of spilling mucin intraabdominally during surgery. Based on the heterogeneous appearance, mucinous content could not be ruled out, while an alternative proposed explanation was bloody content in the cyst. To further examine this and ensure pathological examination of potential malignancy, the MDT-unit decided to proceed with core-needle biopsies towards the solid ¹⁸F-PSMA-PET/CT-suspicious areas, performed by imaging fusion of MRI/Transperineal Ultrasound (TPUS),⁸ and furthermore emptying cystic cavities for 500 mL of bloody-serous fluids. MRI performed eight days later showed modest regression of the cystic component (8.1 x 15.4 × 10.9 cm) indicating fluid regeneration.

Histological analysis revealed Gleason 3+3/ISUP-1 adenocarcinoma in the left-side PSMA-positive biopsy location. Moreover, the rare pSTUMP were considered due to an histologically atypical stroma. The extracted fluids did not contain malignant cells nor mucin.

The MDT-unit decided to offer the patient radical surgical excision. The patient was counseled on the increased surgical risks due to the tumor size.

Robot-assisted radical prostatectomy was performed without complications. Pathological investigation showed pT2c adenocarcinoma (including both prostatic lobes, but limited to the prostate alone), Gleason score 3+4/ISUP 2. The adenocarcinoma was infiltrating an atypical hypercellular stroma composed of different patterns representing pSTUMP. The diagnosis was reinforced by immunohistochemical stain with positive reaction for progesterone receptor. There were no necrosis or stromal mitoses and the Ki67 proliferation rate was <1 %. There was no signs of prostatic stromal sarcoma (PSS) (Fig. 3). Surgical margins were negative.

Fig. 3.

Pathology slides

A: The whitish solid areas representing the adenocarcinoma (black arrows) in the enlarged cystic prostate with multiple collapsed cysts (red arrows).

B: Hematoxylin eosin (HE) stain showing the concurrent tumors. Adjacent irregular glands representing the adenocarcinoma (black arrows) infiltration a hypercellular stroma with epithelioid and fusiform cells with eosinophilic cytoplasm representing pSTUMP (red arrows).

C: Progesterone receptor immunohistochemical (IHC) stain with positive reaction in the stromal tumor.

The patient had a short post-surgical admission and was discharged two days later. At three-months follow-up, PSA was undetectable at < 0.1 ng/mL. He was continent during night-time and morning, however, slightly incontinent during afternoon and evenings and used 2–3 pads per day. Sexual function had not yet been tested.

3. Discussion

Our case report highlights the strength of a multidisciplinary approach in planning treatment of a rare condition with limited evidence-based recommendations. The present diagnostic case depended heavily on the clinical knowledge of the urologists, combined with high-quality diagnostic imaging, performed in both the Radiology and the Nuclear Medicine departments and conclusively on pathological evaluation.

MRI provided information about pelvic anatomy and visualized the heterogeneous tumor, consisting of both cystic and solid compartments, and proposed a GMPC-diagnosis.

¹⁸F-PSMA-PET/CT was performed for primary metastatic staging of the patient. As PSMA is weakly expressed in normal prostate tissue and heavily expressed in cancerous prostate tissue, the solid PSMA-avid areas were considered suspicious of malignancy and acted as indirect guidance for MRI/TPUS-guided core-needle biopsies, that identified the prostatic cancer.⁸

Pathological results of both targeted biopsies and the surgical specimen finally concluded that the cystic tumor was a result of concurrent pSTUMP and adenocarcinoma.

Since both pSTUMP and GMPC can present themselves as enlarged cystic tumors, it was not possible to distinguish them from each other based on diagnostic imaging. Instead the histopathology revealed the two concurrent tumors in a cystic degenerated prostate with histological features different to GMPC.⁶

Regarding surgery, there were preoperative concerns of the technical feasibility of the surgical excision and reconstruction due to the size and location of the prostate. Specifically, it was uncertain whether a tension-free vesicourethral anastomosis could be achieved given the distortion of the pelvis.

The patient was thoroughly counseled on the surgical complexity and the range of possible intraoperative scenarios including bladder augmentation (endocystoplasty) using a segment of the small bowel to reconstruct continuity between the bladder and urethra. Alternatively, if reconstruction proved unfeasible, consent for a cutaneous urinary stoma (Bricker conduit) or an orthotopic neobladder was achieved. No assurances could be made regarding a nerve sparring procedure. Fortunately, a primary tension-free anastomosis was achieved successfully, without injury to the bladder or colon.

The diagnosis of pSTUMP is frequently diagnosed incidentally on needle biopsy or transurethral resection (TURP). Management of pSTUMP with TURP often results in several recurrences⁹. As pSTUMP is able to progress to PSS⁴, with established malignant features and ability to metastasise,⁹ both tumors are preferably treated with radical resection, especially in younger individuals or incidents of enlarged tumors^2,6.

In the present case of concurrent pSTUMP and adenocarcinoma, the management approach of performing radical excision of the cystic prostatic tumor, therefore seems to be the best possible option. This is viewed in the light of the above mentioned literature recommendations regarding pSTUMP, along with the clinical significant symptoms of the patient, the size of the tumor and the patient's age of 50 years. On top of this; prostatectomy was the simultaneous treatment of the concurrent adenocarcinoma.

4. Conclusion

The main message of this rare urological case is that integrating specialized expertise from relevant medical fields enhances the ability to make effective clinical decisions, ultimately leading to the best possible patient outcome.

CRediT authorship contribution statement

Nicolaj Dahl Andersen: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. Mads Ryø Jochumsen: Writing – review & editing, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. Tomas Frahm Nielsen: Writing – review & editing, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. Sofie Møller Graff: Investigation. Kasper Drimer Berg: Writing – review & editing, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. Frederik Ehlern Larsen: Writing – review & editing, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.