Specialized stromal tumors of the prostate: a clinicopathologic study of 50 cases

Mesenchymal Neoplasms of the Bladder and Male Genital Tract, including the Perineum and Scrotum

Mesenchymal neoplasms of the bladder and male genital tract are uncommonly encountered in routine diagnostic practice and present diagnostic challenges. Here, I systematically survey mesenchymal tumors at each body site, including the spermatic cord, scrotum, and perineum. I provide a detailed overview of tumor types that specifically or most commonly occur in the bladder and male genital tract, including pseudosarcomatous myofibroblastic neoplasm of the bladder, proliferative funiculitis, paratesticular sclerosing rhabdomyoma, penile myointimoma, and so-called prostatic stromal tumors.

Interpreting Prostate Multiparametric MRI: Beyond Adenocarcinoma - Anatomical Variations, Mimickers, and Post-Intervention Changes

Prostate magnetic resonance imaging (MRI) is an essential tool in the diagnostic pathway for prostate cancer. However, its accuracy can be confounded by a spectrum of noncancerous entities with similar radiological features, posing a challenge for definitive diagnosis. This review synthesizes current knowledge on the MRI phenotypes of both common and rare benign prostate conditions that may be mistaken for malignancy. The narrative encompasses anatomical variants, other neoplastic processes, inflammatory conditions, and alterations secondary to medical interventions. Furthermore, this review underscores the critical role of MRI quality in diagnostic accuracy and explores the emerging contributions of artificial intelligence in enhancing image interpretation.

Common Diagnostic Challenges in Genitourinary Mesenchymal Tumors: A Practical Approach

Mesenchymal neoplasms within the genitourinary tract include a wide spectrum of tumors, ranging from benign to malignant, and tumors of uncertain malignant potential. Except for stromal tumors of the prostate, which originate from the specific prostatic stroma, these neoplasms generally resemble their counterparts in other body sites. The rarity of these neoplasms and the limitation associated with small biopsy samples present unique diagnostic challenges for pathologists. Accurate diagnosis is paramount, as it significantly influences prognosis and guides management and treatment strategies. This review addresses common diagnostic scenarios, discusses key differential diagnoses, and sheds light on potential diagnostic pitfalls.

Seminal Vesicle Stromal Lipofuscinosis: A Rare Incidental Finding with Potential for Misdiagnosis

We report a patient with isolated stromal lipofuscinosis of the seminal vesicle, a rare entity characterized by intracytoplasmic pigmented granules within stromal cells intimately surrounding seminal vesicle epithelium. Only 4 patients with this unusual phenomenon have been previously reported in the literature. Recognizing this incidental and presumably non-pathologic finding is important to prevent misclassification as a more concerning lesion.

Breast phyllodes tumour with epithelioid feature predisposes to malignant transformation

AIMS

Phyllodes tumours (PTs) are relatively common fibroepithelial tumours comprising epithelial and stromal component. Usually, PTs show a spindle cell morphology with a fibroblast phenotype, while some tumour cells exhibit epithelioid morphological features and sarcomatoid transformation. However, the molecular characteristics of this morphology subset remain unclear. This study aimed to summarise the clinicopathological, morphological and molecular characteristics of seven cases of PT with epithelioid features.

METHODS

Morphological and clinicopathological characteristics were observed and retrieved. Immunohistochemistry, immunofluorescence and electron microscope were performed on seven cases of epithelioid PT to explore immunophenotypic and ultrastructural characteristics. Transcriptomic and proteomic analyses were conducted to compare differentially expressed genes and proteins between epithelioid PT and classical PT.

RESULTS

Patients with epithelioid PT exhibit a high recurrence rate (42.8%). Morphologically, in addition to having epithelioid cytological features, neoplastic stromal cells exhibit moderate to marked atypia and often exhibit sarcomatoid transformation, similar to the characteristics of borderline PT. Transcriptomic and proteomic analyses demonstrated that epithelioid PTs are distinct from classical PTs in gene expression and protein abundance levels. Immunohistochemical analysis showed that among all differentially expressed proteins, epithelioid PT showed abnormal p16/retinoblastoma expression patterns, similar to those of malignant PT.

CONCLUSIONS

Epithelioid PT has unique morphological characteristics, biological behaviour and protein expression profile, which meets the diagnostic criteria of borderline PT and is prone to sarcomatoid transformation. It may be a special morphological subgroup of borderline PT and has partial characteristics of malignant PT, which should be taken seriously in pathological diagnosis and clinical management.

Prostatic stromal tumor of uncertain malignant potential: a case report and literature review

Prostatic stromal tumors, encompassing prostatic sarcoma and stromal tumors of uncertain malignant potential (STUMP), represent an exceedingly rare category of prostatic diseases, with a prevalence of less than 1%. We present a rare case involving a man in his early 40s diagnosed with STUMP. Despite presenting with normal prostate-specific antigen (PSA) concentrations, the patient experienced persistent dysuria and gross hematuria for >7 months, leading to an initial misdiagnosis of benign prostatic hyperplasia. Persistent symptoms prompted further investigation, with magnetic resonance imaging (MRI) revealing a suspicious lesion on the left side of the prostate, initially thought to be malignant. Transrectal prostatic biopsy subsequently confirmed the presence of mucinous liposarcoma, with no medical history of diabetes, coronary heart disease, or hypertension. The treatment approach comprised robot-assisted laparoscopic radical prostatectomy, culminating in a postoperative pathological definitive diagnosis of STUMP. This case underscores the indispensable role of early MRI in the diagnostic process, highlighting the necessity of detailed pathological examination for a conclusive diagnosis. Our report aims to illuminate the diagnostic challenges and potential treatment pathways for STUMP, emphasizing its consideration in the differential diagnosis of prostatic tumors to advance clinical outcomes in this rare but important condition.

Prostatic stromal tumour of uncertain malignant potential in a dog

An 11-year-old male Miniature Dachshund dog was presented with dyschezia. Computed tomography examination 35 days after the initial visit revealed a prostate mass (4.0 × 3.5 × 2.7 cm) and prostatectomy and orchiectomy were performed 13 days later. Grossly, the prostate was rubbery and the cut surface of the mass was swollen. The mass was whitish and demarcated from the surrounding tissues. Microscopically, the mass had a capsulate consisting of atypical spindloid stromal cells arranged in a phyllode pattern and also in a fasciculated pattern admixed with acinar ductal cells. Atypical stromal cells contained round-to-oval finely hyperchromatic nuclei that had distinct nuclei and abundant eosinophilic cytoplasm. Immunohistochemically, the atypical stromal cells were positive for vimentin, CD34, desmin, α-smooth muscle actin, progesterone receptor and androgen receptor but negative for cytokeratin AE1/AE3, p63, c-Kit, DOG-1 and SOX10. On the basis of these findings, the tumour was diagnosed as a prostatic stromal tumour of uncertain malignant potential.

Primary Paraganglioma of the Prostate: A Systematic Review of the Literature for A Rare Entity

BACKGROUND

Paragangliomas of the urinary tract are exceptionally uncommon, and sporadic case reports of primary paraganglioma of the prostate have been reported in the literature.

METHODS

Systematic research in PubMed/Medline and Scopus databases concerning primary prostatic paraganglioma was performed by two independent investigators.

RESULTS

This analysis included 25 adult males, with a mean age of 49.8 ± 22.4 years. 32% of included patients had a history of hypertension. Problems during urination (52%), blood loss (44%), either as hematuria or hemospermia, and catecholamine-related symptoms (36%) comprised the most frequently reported clinical manifestations. Digital rectal examination found a palpable nodule in 36% of patients, while prostatic specific antigen (PSA) was normal in all tested patients. Abdominal ultrasound (44%), computed tomography (44%) and magnetic resonance imaging (28%) helped to identify the primary lesion. 24-hour urine epinephrine, norepinephrine and vanillylmandelic acid (VMA) levels were elevated in 90%, 80% and 90% of included patients. Open surgical excision of the mass was performed in 40%, transurethral resection in 8%, open radical prostatectomy in 24%, transurethral resection of the prostate in 16% and robot-assisted radical prostatectomy in 4% of included patients.

CONCLUSION

Due to atypical clinical manifestation and scarcity of prostatic paraganglioma, urologists should be aware of this extremely rare entity.

Prostatic stromal tumour of uncertain malignant potential treated with robotic-assisted radical prostatectomy: medium-term oncological and functional outcome of two cases

Stromal tumour of uncertain malignant potential (STUMP) is a rare tumour of the prostate with variable and unpredictable risk and clinical progression. There is no clear consensus on how it should be managed. We describe two cases of patients who presented to their general practitioners with raised prostate-specific antigen in one instance and an abnormal digital rectal examination in the other. Biopsies were carried out and a diagnosis of STUMP was made. Both cases were managed with robot-assisted radical prostatectomy and after 4.8 years of follow-up, there has not been any recurrence. This is the first reported UK case in which STUMP has been successfully managed with robotic surgery with excellent medium-term results. Radical prostatectomy can be used to treat STUMP tumour with good oncological and functional outcomes.

Prostatic stromal sarcoma: A case report and literature review

Stromal sarcoma of the prostate is extremely rare. In this article, we report the case of a 43-year-old male admitted to the local hospital due to dysuria. Although the pathological findings from transurethral prostatic resection showed low-grade stromal sarcoma, the surgical specimen after radical prostatectomy revealed high-grade sarcoma with hypercellularity, marked atypical spindle cells, and high mitotic activity. This case study and literature analysis aim to emphasize its rarity and raise awareness about clinical and pathological diagnosis.

Prostatic stromal sarcoma: Report of a rare case in a young male and review of the literature

INTRODUCTION AND IMPORTANCE

Common prostatic neoplasms are diagnosed frequently, whereas rare entities require particular awareness and special clinical management.

CASE PRESENTATION

A 31-year-old man presented with dysuria, hematuria and urinary retention. Histomorphological analysis of material obtained by transurethral resection of the prostate initially favored a sarcomatoid carcinoma, but immunohistochemistry allowed the correct diagnosis of sarcoma of the specialized stroma of the prostate.

CLINICAL DISCUSSION

The patient refused surgical treatment and, despite chemotherapy, he died 8 months after the diagnosis. Herein, we will highlight the diagnostic and therapeutic challenge of prostatic stromal sarcoma by illustrating this case and reviewing the relevant literature.

CONCLUSION

Although rare and shadowed by more common neoplasms that may mimic it, prostatic stromal sarcoma should be considered in the differential diagnosis of bladder and prostate neoplasms because of its dismal prognosis.

A Retroprospective Clinicopathological Study of Prostatic Lesions in Surgical Specimens

Background Prostatic diseases such as inflammation, benign prostatic hyperplasia, and tumors are prime causes of mortality and morbidity in males. The prevalence of these lesions increases with advancing age. The second most common cancer among males is prostate cancer, next to lung cancer worldwide.

Aim The present study was undertaken with the aim of studying the clinicopathological characteristics of prostate lesions in surgical specimens

Methods The present study was a retroprospective study. A total of 212 prostate surgical specimens were included. Information provided in the requisition form regarding age, type of prostatic biopsy and clinical presentation, and histopathological diagnosis was taken into consideration and recorded. All specimens were fixed in 10% neutral buffered formalin and 5μ sections were stained with hematoxylin and eosin stain (H&E stain). Relevant clinical data including age, the presenting complaints, and S.PSA values were recorded. Data were collected and analyzed using simple statistical methods with Microsoft Excel 2016.

Results Out of 212 cases analyzed, 161 (76%) were transurethral resection of prostate (TURP) TUPR specimens, 38 (18%) were trucut needle biopsies, and 13 (6%) were open prostatectomy specimens. The youngest patient was 48 years old while the oldest patient was 90 years old with a mean of 71.7  ± 8.2 years. Of the total 212 surgical specimens, 174 (82%) cases were of benign prostatic hyperplasia (BHP), and 38 (18%) were prostatic adenocarcinoma (PAC). Also, 94 (44.3%) of BPH and carcinoma of the prostate cases were most common in the seventh decade of life (61-70 years). Difficulty in micturition was the most common presentation 82 (39%). A maximum number of the BPH cases 81 (46.5%) had the prostate-specific antigen range of 0 to 4 ng/mL. The highest value of serum PSA was noted among the PAC patients in the range of > 80 ng/mL. Out of 38 cases of prostatic adenocarcinoma, moderately differentiated (Gleason scores 7) was the most common core and was seen in 42.1% of the PAC cases.

Conclusion The present study showed that the most frequently encountered prostatic lesion was BHP, commonly seen in the age group of 61 to 70 years. The PAC was common among males of more than 60 years. Histopathological examination is the best diagnostic tool for PAC

A Rare Case of Prostatic Stromal Tumour of Uncertain Malignant Potential Surrounding Ejaculatory Ducts in a Patient With Concurrent Prostate Adenocarcinoma

Stromal tumour of uncertain malignant potential (STUMP) is exceedingly rare. Diagnosis and management of STUMP present a challenge to the urologist due to the absence of specific clinical findings and its unpredictable clinical course. Thus, radical resection is often recommended. Here, we present a case of a 64-year-old male, who presented with mild obstructive voiding symptoms with a raised age-specific prostate-specific antigen (PSA) of 3.1. Magnetic resonance imaging (MRI) showed an area of suspicion, in an area thought to be the left seminal vesicle, containing a malignant lesion within it. Biopsy of this area and the prostate confirmed concurrent prostatic STUMP and Gleason 3+3=6 adenocarcinoma of the prostate, managed with robotic-assisted laparoscopic radical prostatectomy with wide local excision.

Prostatic Malakoplakia: Clinicopathologic Assessment of a Multi-institutional Series of 49 Patients

Prostatic MP is rare, with only case reports and small series (<5 patients) available in the literature. In this study we analyzed an international multi-institutional series of 49 patients with prostatic MP to better define its clinicopathologic features. The median age was 67 years, and the median serum PSA was 7.5 ng/mL. MP was clinically manifest in most cases (28/45 patients with data available, 62%). Of 43 patients with detailed clinical history available, 21 (49%) had concurrent or metachronous malignancies (including prostate cancer). Diabetes or insulin resistance was present in 11 patients (26%). Additionally, 3 patients had a history of solid organ transplantation and 1 had HIV. Of note, 6/34 patients (18%) without concurrent prostate cancer had an abnormal digital rectal examination or PIRADS ≥ 4 lesions on MRI. The initial diagnosis was made on core biopsies (25/49, 51%), transurethral resection specimens (12/49, 24%), radical prostatectomies (10/49, 20%), Holmium-laser enucleation (1/49, 2%) and cystoprostatectomy (1/49, 2%). Tissue involvement was more commonly diffuse or multifocal (40/49, 82%). Von Kossa and Periodic acid-Schiff stains were positive in 35/38 (92%) and 26/27 lesions (96%), respectively. Of note, 2 cases were received in consultation by the authors with a preliminary diagnosis of mesenchymal tumor/tumor of the specialized prostatic stroma. In conclusion, the present study, which is the largest to date, suggests that prostatic MP often manifests with signs and symptoms that may mimic those of prostate cancer in a subset of patients. Moreover, MP may be found incidentally in patients with concurrent prostate cancer.

Magnetic resonance imaging features of prostatic stromal tumour of uncertain malignant potential

INTRODUCTION

Prostatic stromal tumours of uncertain malignant potential (STUMPs) are rare prostate tumours. The purpose of this study was to investigate the magnetic resonance imaging features of STUMPs.

METHODS

A total of 12 patients with STUMP confirmed with pathology who underwent MRI from 2012 to 2020 were retrospectively reviewed. Pathological characteristics including histopathology and immunohistochemistry were also recorded.

RESULTS

Among 12 STUMPs, the tumours were detected in the peripheral zone (41.7%[n = 5]) and transitional zone (58.3% [n = 7]) of the prostate. 8 cases (66.7%) were round shape. All lesions were well-defined and compressed the adjacent structures but without signs of an invasion. Homogeneous T1WI and heterogeneous T2WI signals were observed in the STUMPs. The tumours were mainly composed of solid components, while intratumoral cystic change (58.3%[n = 7]) and haemorrhage (8.3%[n = 1]) were seen. 10 cases(83.3%) were seen as relatively high DWI signal, while 2 cases(16.7%) with no increase in DWI. The mean ADC value was 1.084 ± 0.193 (range: 0.864-1.489 × 10^-3  mm² /s). STUMPs had heterogeneous enhancement, with persistent or gradual enhancement. In immunohistochemical staining, Vim, CD34, PR and SMA were positive in the majority of STUMPs.

CONCLUSION

MRI features of STUMP are presented as regular, well-defined and isolated prostatic mass with intact pseudocapsule. The presence of heterogeneous T2WI signal, intratumoral cystic change, slightly low mean ADC value and persistent or gradual enhancement may help predict the STUMPs.

Mesenchymal Neoplasms of the Prostate and Seminal Vesicles: Spectrum of Disease with Radiologic-Pathologic Correlation

There is a wide spectrum of benign and malignant mesenchymal neoplasms of the prostate, which account for less than 1% of all prostatic tumors. These include distinctive tumors that arise from the specialized prostatic stroma and site-agnostic neoplasms such as smooth muscle tumors, fibrous or myofibroblastic neoplasms, neurogenic tumors, vascular tumors, and a plethora of sarcomas. Select tumors show classic sites of origin within the prostate. While stromal tumors of uncertain malignant potential (STUMPs) commonly involve the peripheral zone at the prostate base, leiomyomas typically originate from the central prostate toward the apex. Some "prostatic" neoplasms such as gastrointestinal stromal tumors, solitary fibrous tumor (SFT), paragangliomas, and neurogenic tumors arise primarily from periprostatic soft tissues. Most mesenchymal tumors of the prostate and seminal vesicles manifest as large tumors that cause nonspecific symptoms; prostate-specific antigen level is not typically elevated. Diverse mesenchymal neoplasms demonstrate characteristic histopathologic and immunocytochemical features and variable cross-sectional imaging findings. While leiomyoma and SFT typically display low signal intensity on T2-weighted images, synovial sarcomas commonly show hemorrhage. Diagnosis is difficult because of the rarity and lack of awareness of the tumors and the significant overlap in histopathologic features. Select tumors show characteristic genetic abnormalities that allow the diagnosis to be established. For example, more than 90% of SFTs are characterized by a unique NAB2-STAT6 gene fusion, and more than 95% of synovial sarcomas are associated with a distinctive SYT-SSX chimeric transcript. Accurate diagnosis is imperative for optimal management owing to markedly different tumor biology as well as attendant therapeutic and prognostic implications. While STUMPs commonly recur, sarcomas typically charter an aggressive course with poor prognosis. Online supplemental material is available for this article. ^©RSNA, 2022.

ARID1A deficient undifferentiated spindle cell and rhabdoid sarcoma of the prostate: report of a unique case with emphasis on diagnostic implications

Background

SWItch Sucrose Non-Fermentable (SWI/SNF) chromatin-remodeling complex functions collectively as a tumor suppressor and the inactivation of any of its constituent components is frequently associated with tumor initiation and/or progression. Most SWI/SNF deficient tumors share common rhabdoid morphology. ARID1A is the most frequently dysregulated SWI/SNF subunit in human cancer and inactivation of ARID1A is frequent across carcinomatous types while very rarely drives the tumorigenesis of sarcomas. Herein, we report a rare case of primary prostatic undifferentiated spindle cell sarcoma with focal rhabdoid morphology, harboring biallelic inactivation of ARID1A detected by next-generation sequencing with complete loss of ARID1A expression by immunohistochemistry.

Case presentation

The patient is a 58-year-old man who presented with dysuria and obstructive voiding symptoms for 3 month and was found to have a large, ill-defined, prostatic mass lesion with circumferential extension into the rectal wall on imaging studies. A needle biopsy showed a spindle cell undifferentiated sarcoma of the prostate and the patient was treated by chemotherapy of combined etoposide and cisplatin for 2 months. A subsequent imaging study showed that the tumor was significantly enlarged, and the patient underwent laparoscopically radical prostatectomy. Gross examination showed a disrupted, 10 × 7 × 5 cm, solid and cystic mass involving almost the entire prostate and sparing the seminal vesicle glands. Histologic examination showed that tumor was composed mainly of mildly atypical, oval to spindle-shaped cells, arranged in sheets and fascicles or herringbone-like patterns within a small amount of edematous to myxoid, vascularized stroma. Notably, groups of discohesive rhabdoid tumor cells with eccentric nuclei, prominent nucleoli, and abundant globular cytoplasm were observed. There were prominent mitotic figures, multifocal geographic necroses, and foci of lymphovascular invasion. Immunohistochemistry showed that the tumor cells were diffusely positive for TLE-1 and vimentin and focally positive for epithelial membrane antigen, AE1/3, Cam5.2, SATB2, and CD34 (all in less than 10% tumor cells). Next-generation sequencing showed biallelic inactivation mutation of ARID1A; the predicted inactivating effect of ARID1A deletion was confirmed by immunohistochemical staining. After the surgery, the patient received an alternative combined chemotherapy of doxorubicin and ifosfamide for 5 months. The patient died 9 months after initial presentation due to extensive abdominal metastases.

Conclusions

We report an ARID1A deficient undifferentiated spindle cell and rhabdoid sarcoma of the prostate, adding to the growing spectrum of SWI/SNF driven undifferentiated sarcoma. Rhabdoid cells can be a helpful morphological clue for promoting molecular and immunohistochemical analyses for deficiency of SWI/SNF subunits, in the diagnostic workup of undifferentiated neoplasms featuring epithelioid or rhabdoid morphology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13000-022-01198-4.

Solitary Fibrous Tumor With Extensive Epithelial Inclusions

OBJECTIVES

Solitary fibrous tumor (SFT) harboring extensive epithelial inclusions is rare and can stimulate a biphasic neoplasm composed of epithelial and stromal elements.

METHODS

Three cases of SFT with extensive epithelial inclusions were retrieved. H&E stain, immunohistochemical stain, and targeted next-generation sequencing were performed.

RESULTS

There were two male patients and one female patient aged 54, 32, and 68 years. All tumors were located in abdominopelvic sites involving the kidney (case 1), omentum (case 2), and prostate (case 3), respectively. Microscopically, all tumors were circumscribed and composed of a background of SFT admixed with randomly embedded glands or cysts, organizing sometimes in a phyllodes-like architecture. The covered epithelium displayed a range of morphologies from simple cystic to stratified and to complex papillary proliferation. Immunohistochemically, both STAT6 and CD34 were expressed in the spindle cells but not in the epithelial inclusions. RNA sequencing revealed fusions involving NAB2~STAT6 in all cases. DNA sequencing demonstrated TERT c.-124C>T mutation in case 1. Prognostic stratification scores were intermediate in case 1 and low in cases 2 and 3.

CONCLUSIONS

SFT with extensive epithelial inclusions represents a rare but potentially underrecognized variant of SFT and shows compatible molecular features with conventional SFT.

A case of incidental STUMP discovery in a patient with concurrent prostatic adenocarcinoma

Stromal tumours of the prostate are exceedingly rare, often presenting in patients in their fifth decade of life. They are classified as either stromal sarcomas, or stromal tumours of uncertain malignant potential (STUMP), the latter of which is known to have diverse clinical behaviour and thus surgical excision is often warranted. We present a case of a 71-year-old male, initially worked up by his family doctor due to mild obstructive voiding symptoms. Following a more thorough urologic workup, including a prostate biopsy, he was found to have a markedly elevated prostate specific antigen and positive cores on prostate biopsy demonstrating prostatic adenocarcinoma. The decision was made to treat with retropubic radical prostatectomy and bilateral pelvic lymph node dissection. Resulting pathology showed concurrent prostatic adenocarcinoma in addition to STUMP. The patient continues to be followed by oncology as well as a sarcoma specialist due to the unique nature of his case.

Re-evaluating tumors of purported specialized prostatic stromal origin reveals molecular heterogeneity, including non-recurring gene fusions characteristic of uterine and soft tissue sarcoma subtypes

Tumors of purported specialized prostatic stromal origin comprise prostatic stromal sarcomas (PSS) and stromal tumors of uncertain malignant potential (STUMP). Prior studies have described their clinicopathologic characteristics, but the molecular features remain incompletely understood. Moreover, these neoplasms are morphologically heterogeneous and the lack of specific adjunctive markers of prostatic stromal lineage make precise definition more difficult, leading some to question whether they represent a specific tumor type. In this study, we used next-generation DNA and RNA sequencing to profile 25 primary prostatic mesenchymal neoplasms of possible specialized prostatic stromal origin, including cases originally diagnosed as PSS (11) and STUMP (14). Morphologically, the series comprised 20 cases with solid architecture (11 PSS and 9 STUMP) and 5 cases with phyllodes-like growth pattern (all STUMP). Combined DNA and RNA sequencing results demonstrated that 19/22 (86%) cases that underwent successful sequencing (either DNA or RNA) harbored pathogenic somatic variants. Except for TP53 alterations (6 cases), ATRX mutations (2 cases), and a few copy number variants (-13q, -14q, -16q and +8/8p), the findings were largely nonrecurrent. Eight gene rearrangements were found, and 4 (NAB2-STAT6, JAZF1-SUZ12, TPM3-NTRK1 and BCOR-MAML3) were useful for reclassification of the cases as specific entities. The present study shows that mesenchymal neoplasms of the prostate are morphologically and molecularly heterogeneous and include neoplasms that harbor genetic aberrations seen in specific mesenchymal tumors arising in other anatomic sites, including soft tissue and the uterus. These data suggest that tumors of purported specialized prostatic stromal origin may perhaps not represent a single diagnostic entity or specific disease group and that alternative diagnoses should be carefully considered.

Differential diagnosis of uncommon prostate diseases: combining mpMRI and clinical information

The differential diagnosis of abnormalities in the prostate is broad, covering common (acinar adenocarcinoma, benign prostatic hyperplasia, chronic prostatitis, hemorrhage, cysts, calcifications, atrophy and fibrosis) and less common conditions (tumors other than acinar adenocarcinoma, granulomatous prostatitis containing tuberculosis, abscesses and other conditions, and idiopathic disorders such as amyloidosis and exophytic benign prostatic hyperplasia). Recent advances in magnetic resonance imaging (MRI) of the prostate gland and imaging guidelines, such as the Prostate Imaging Reporting and Data System version 2.1 (PI-RADS v2.1), have dramatically improved the ability to distinguish common abnormalities, especially the ability to detect clinically significant prostate cancer (csPCa). Overlap can exist in the clinical history and imaging features associated with various common/uncommon prostate abnormalities, and biopsy is often required but is invasive. Prostate abnormalities can be divided into two categories: category 1, diseases for which PI-RADS scores are suitable for use, and category 2, diseases for which PI-RADS scores are unsuitable for use. Radiologists must have an intimate knowledge of other diseases, especially uncommon conditions. Past relevant history, symptoms, age, serum prostate-specific antigen (PSA) levels, MRI manifestations, and the applicability of the PI-RADS assessment should be considered when diagnosing prostate abnormalities.

Prostate stromal tumor with prostatic cysts after transurethral resection of the prostate: A case report

BACKGROUND

A prostatic stromal tumor is deemed to be a rare oncology condition. Based on the retrospective analysis of clinical data and scientific literature review, a case of prostatic stromal tumor was reported in this article to explore the diagnosis, treatment and prognosis of this rare disease.

CASE SUMMARY

The present case involved an older male patient who was admitted to our department for a medical consultation of dysuria. Serum prostate-specific antigen was 8.30 ng/mL, Ultrasound and magnetic resonance imaging suggested evident enlargement of the prostate and multiple cystic developments internally. Considering that the patient was an elderly male with a poor health status, transurethral resection of the prostate was performed to improve the symptoms of urinary tract obstruction. Furthermore, based on histopathologic examination and immunohistochemical staining, the patient was pathologically diagnosed with prostatic stromal tumor. The patient did not receive any further adjuvant therapy following surgery leading to a clinical recommendation that the patient should be followed up on a long-term basis. However, during the recent follow-up assessment, the patient demonstrated recurrence of lower urinary tract symptoms and gross hematuria.

CONCLUSION

Referring to scientific literature review, we believe that the management of these lesions requires a thorough assessment of the patient. Furthermore, the treatment of prostate stromal tumors should be based on the imaging examination and pathological classification. Active surgical treatment is of great significance to the prognosis of patients, and subsequent surveillance after the treatment is warranted.

18F-FDG PET/CT Imaging of Prostate Stromal Tumor of Uncertain Malignant Potential

ABSTRACT

A 79-year-old man presented with dysuria and increased serum prostate-specific antigen level (21 ng/mL). MRI revealed bulky prostate enlargement but was inconclusive in revealing neoplastic lesions. Nevertheless, because of high clinical suspicion for neoplasm, transrectal biopsy revealed stromal tumor of uncertain malignant potential mixed with foci of low-grade primitive prostate stromal sarcoma. 18F-FDG PET/CT showed high FDG uptake consistent with neoplasm in the lower part of the hypertrophic prostate gland and focal areas of elevated FDG uptake, consistent with metastases in the spine, ribs, and femur.

Imaging of non-epithelial neoplasms of the prostate

The purpose of this article is to review the spectrum of rare non-epithelial tumors of the prostate. This focused article will help the readers to understand the imaging findings of such rare entities attributed to their clinicopathological features. Radiologists must be familiar with the spectrum of non-epithelial tumors of the prostate, which helps to suggest alternate diagnosis other than adenocarcinoma, when imaging features are atypical. This is important because these tumors have different management approaches and prognoses when compared to adenocarcinoma of the prostate.

Prostatic stromal proliferations: a review

Prostatic stromal proliferations account for the majority of benign tumour-like lesions in the prostate. The most common is nodular hyperplasia, seen in a majority of elderly men. Diagnostic difficulty is encountered with some variants, including stromal hyperplasia with atypia, characterised by degenerative changes of myofibroblasts. In contrast with benign stromal tumours, malignant stromal tumours of the prostate are rare, accounting for less than 0.1% of all prostatic malignancies. The most common are rhabdomyosarcoma (paediatric) and leiomyosarcoma (adults); others include phyllodes tumour and stromal sarcoma. Some authors lump malignant tumours with poor outcome (e.g., phyllodes tumour and stromal sarcoma) with benign stromal tumours (e.g., stromal hyperplasia with atypia, leiomyoma), considering them collectively to be of uncertain malignant potential, but this approach is discouraged. This review presents a contemporary approach to classification and diagnosis of prostatic stromal tumours.

Case of prostate stromal tumour of uncertain malignant potential where positron emission tomography with 18F-fluorodeoxyglucose was useful for surgical planning

Stromal tumour of uncertain malignant potential of the prostate is a rare tumour with a variable clinical behaviour ranging from incidentally detected indolent tumours that never progress, to aggressive diseases almost identical to sarcomas that may invade surrounding organs or develop metastases. Surgical excision is generally recommended for local diseases; however, owing to its diverse clinical outcomes, optimal management may vary from surgery alone to wide excision combined with chemotherapy and/or radiotherapy. Therefore, preoperative evaluation of the malignant potential of the disease is essential to decide the treatment strategy. Herein, we report a case of stromal tumour of uncertain malignant potential successfully treated with minimally invasive robot-assisted radical prostatectomy alone under the diagnosis of the disease with low malignant potential based on the findings of positron emission tomography with 18F-fluorodeoxyglucose.

Primary Gastrointestinal Stromal Tumor of the Prostate: Unexpected Guest

Primary mesenchymal lesions of the prostate are exceptionally rare. They comprise 1% of all prostatic neoplasms. Despite its rare location, the diagnosis of primary gastrointestinal stromal tumors (GISTs) of the prostate gland should never be missed. Such a diagnosis can be made after the rolling out of direct extension from adjacent organs, especially the rectum. GIST diagnosis has a clinical impact on patient treatment and clinical outcomes. They harbor a certain KIT activation mutation that responds to pharmacologic therapy inhibitors.

The objective of the current study was to provide a thorough review of GIST arising primarily in the prostate gland along with a comprehensive study of GIST pathogenesis, histologic morphology, immunohistochemistry, and molecular studies’ findings, and their importance in differentiating GIST from other prostate mesenchymal tumors. This will emphasize the role of careful spindle cell lesion diagnosis in the prostate gland that can influence the prognostic stratification of clinical management, future follow-up, and disease outcome.

Thirteen cases were collected after an extensive and detailed review of the English literature through PubMed, Medknow, Google Scholar, as well as personal experience.

The anatomic location of this lesion plays a significant role in the differential diagnosis. It is difficult to establish the accurate primary origin of GIST on core needle tissue biopsy. Thus, clinical, and radiological examinations play a crucial role in rolling out the possibility of rectal GIST secondarily invading and involving the prostate gland.

To conclude, primary prostatic GIST is a rare diagnosis. Extraintestinal, particularly rectal, GIST can clinically and radiologically mimic the impression of the prostatic lesion. Before diagnosing primary prostatic spindle cell lesions, such as solitary fibrous tumor (SFT), inflammatory myofibroblastic tumor (IMT), leiomyoma, leiomyosarcoma, or prostatic stromal tumors, one should include CD117/c-Kit in the workup of a prostatic spindle cell lesion. GIST has distinct pathogenesis, and its diagnosis can have a clinical impact on the patient's management plan and clinical outcome.

Uncommon Prostate Malignant Neoplasms

Prostate adenocarcinoma is the most common prostate cancer; however, there are several other malignant neoplasms that radiologists should be familiar with. The histological classification of malignant prostate neoplasms includes epithelial tumors, mesenchymal tumors, neuroendocrine tumors, hematolymphoid tumors, and stromal tumors. Knowledge of the main clinical and prostate magnetic resonance imaging features of uncommon tumors beyond adenocarcinoma is important for radiologists to enlarge their diagnostic ability and guide referring physician regarding the appropriate patient workup.The aim of this review article is to (1) review the main anatomical and histological concepts of the prostate gland and (2) provide an overview of uncommon prostate malignant neoplasms, emphasizing the key clinical, pathological, and imaging findings that may help radiologists in their daily interpretation of prostate magnetic resonance imaging.

[A clinical analysis of 14 cases of prostatic stromal tumor of uncertain malignant potential]

OBJECTIVE

To investigate the clinical and pathologic characteristics, diagnosis, treatment, prognosis and survival of prostatic stromal tumor of uncertain malignant potential.

METHODS

Overall 14 patients with prostatic stromal tumor of uncertain malignant potential were treated from October 2008 to April 2020, the patient age ranged from 27 to 78 years (mean 54 years). The disease duration was 1 to 180 months (mean duration of 46 months). The clinical manifestations mainly included urinary obstructive symptoms and urethral irritating symptoms. The tumors were located in the peripheral zone or the transition zone. Digital rectum examination indicated prostatic tumor. Serum prostatic specific antigen level was always normal or elevated. Transrectal ultrasonography and magnetic resonance imaging indicated prostatic tumor. Magnetic resonance imaging in showed large, round, well-defined masses, which were diffusely heterogeneous signal on T2 weighted imaging. Following the administration of intravenous contrast medium, the lesion had diffuse and heterogeneous enhancement.

RESULTS

In the study, 3 cases underwent prostate biopsy, 2 cases underwent transurethral resection of the prostate, 9 cases underwent radical excision or transurethral resection of the prostate with definite diagnosis of pathologic features. Under the light microscope, the interstitial cells of stromal tumor of uncertain malignant potential were overgrowth and fusiform cells showed some degree of pleomorphism, nuclei with few mitotic figures, and necrosis was not often seen. Immunohistochemical staining showed that prostate specific antigen was negative, while vimentin was positive in the tumor tissue, CD34, progesterone receptor and smooth muscle actin were positive in the majority, and Ki67 positive index was 1%-20% (mean 6%). Twelve cases were followed-up, and the time of survival varied from 10 to 96 months (mean 65 months), two cases were lost to the follow-up, one case died of disease at the end of 10 months, nine cases were free of disease recurrence after surgery, two cases underwent more transurethral resection of the prostate due to local recurrence.

CONCLUSION

STUMP is a very rare tumor of the specialized prostatic stroma with an unpredictable clinical behavior. The clinical manifestations, transrectal ultrasonography and magnetic resonance imaging are valuable for the diagnosis of prostatic stromal tumor of uncertain malignant potential. Its definite diagnosis depends on pathological examination. Up to now, early surgery and combined therapy are effective treatments for prostatic stromal tumor of uncertain malignant potential.

Malignant solitary fibrous tumour of the prostate: four cases emphasising significant histological and immunophenotypical overlap with sarcomatoid carcinoma

Solitary fibrous tumour (SFT) is well-described in the urinary tract, but malignant examples are rare. We studied our experience with high grade malignant SFT of the prostate to address the degree of histological and immunophenotypical overlap with sarcomatoid carcinoma and prostatic stromal sarcoma. Four cases were identified from the surgical pathology consultation archives. All available H&E stained sections were reviewed. Immunostains for STAT6, CAM5.2, NKX3.1, PAX-8, GATA3, high molecular weight cytokeratin (34BE12), p40, and p63 were performed on available material. Each case was evaluated by three separate SFT prognostic risk models based on clinicopathological features, and for features of 'dedifferentiated SFT'. The patient's ages were 49, 55, 69, and 73 years. Three presented with symptoms of benign prostatic hyperplasia and one with haematuria. Tumour sizes were 5, 9, 13, and 13 cm. Mitotic rate ranged from 6 to 20 mitoses per 10 high power fields, and two cases showed abrupt transition from conventional SFT to areas with marked nuclear pleomorphism/anaplasia (i.e., 'de-differentiation'). Immunophenotypically, all four cases had strong and diffuse nuclear reactivity for STAT6. For other markers, three of three had both focal PR and GATA3 nuclear expression (up to 30% of cells). One case with 'dedifferentiated' features showed expression of multiple epithelial markers, including EMA (focal), high molecular weight cytokeratin (focal), p63, and p40. In summary, malignant SFT may rarely occur in the prostate and may closely mimic sarcomatoid carcinoma or prostatic stromal sarcoma, both histologically and immunophenotypically. Consideration of the diagnostic possibility of malignant SFT, recognition of unexpected GATA3 and PR expression, and utilisation of monoclonal STAT6 immunohistochemistry facilitate appropriate diagnosis at this unusual anatomical site.

CT and MRI findings of a stromal tumour of uncertain malignant potential of the prostate

Cystic neoplasms arising from the prostate are rare, and stromal tumours of uncertain malignant potential and the spectrum of cystic epithelial tumours of the prostate are the major differential diagnoses of a cystic prostatic neoplasm. We report a case of a stromal tumour of uncertain malignant potential, which showed a multilocular cystic mass with some solid components. The solid component of the tumour did not show substantial diffusion restriction and uptake of ¹⁸F-FDG-PET, and this could be the critical finding suggesting a stromal tumour of uncertain malignant potential rather than a malignant cystic epithelial tumour.

Clinicopathologic characteristics of prostatic stromal sarcoma with rhabdoid features: A case report

BACKGROUND

Prostatic stromal sarcoma presenting with rhabdoid features is extremely rare, and only four cases have been reported in the English-language literature to date. Accordingly, there is no absolute definition of this group of tumors as yet, and our overall understanding of its morphological features, therapeutic regimen and prognosis is limited.

CASE SUMMARY

A 34-year-old male patient was referred to our hospital to address a 2-mo history of hematuria and progressive dysuria. Pelvic computed tomography scan revealed a 6.0 cm × 5.2 cm × 7.2 cm mass in the prostate, with bladder invasion. The patient underwent transurethral prostatectomy as upfront therapy. He refused further treatment and died of uncontrollable tumor growth 3 mo after surgery. Pathology analysis revealed the stroma to be pleomorphic, with a huge number of atypical spindle cells. Rhabdomyoblastic cells, with abundant eosinophilic cytoplasm, were detected. The spindle cells were positive for vimentin, INI1 and β-catenin, and the rhabdomyoblastic cells were positive for MyoD1, myogenin and INI1. The spindle cells and epithelial cells were sporadically positive for P53.

CONCLUSION

The prostatic stromal sarcoma tumor was immunoreactive for β-catenin, suggesting a role for the Wnt/β-catenin pathway in this tumor type.

Two Cases of Spindle Cell Neoplasms in Patients Undergoing Holmium Laser Enucleation of the Prostate

Background: Holmium laser enucleation of the prostate (HoLEP) has proven to be effective in benign proliferations of the prostate resulting in large prostatic volumes. It is a less-invasive surgical alternative to transurethral resection and surgical resection. Prostatic adenocarcinoma can incidentally be found in the enucleated tissue. Occasionally, nonadenocarcinomatous forms of neoplasia occur such as sarcoma. Case Presentation: Two male patients, both 65 years old, undergo HoLEP for gigantic prostates. The first patient presented with recurrent hematuria and clot retention. After HoLEP, the patient voiding symptoms improved. Pathologic immunostaining of the tissue showed spindle cell proliferation consistent with stromal tumor of uncertain malignant potential (STUMP). The second patient presented with acute urinary retention and subsequently underwent HoLEP. Pathologic examination of the enucleated tissue was consistent with prostatic stromal sarcoma. Conclusion: HoLEP is a well-established surgical treatment for gigantic proliferations of benign prostatic tissue. Occasionally, patients who are candidates for HoLEP may have a rare underlying pathologic condition such as a sarcoma or a STUMP. Exclusion of underlying malignant processes in massive prostates is necessary before operating.

Stumped by rapid symptomatic prostatic regrowth: A case report on a STUMP tumour of the prostate resected with HoLEP

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Stromal tumour of Undetermined malignant potential (STUMP) of the prostate is a rare tumour arising from the prostate specialized stroma.

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The patient presented with LUTS, MRI showed prostatic growth, and biopsy showed no malignancy.

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The symptoms were treated by TURP and 11 g were removed of the prostate.

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The tumour recurred within less than a year to three times its original size.

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It is the first time in literature, HoLEP was used to remove the origin of the tumour successfully.

Introduction

Stromal Tumour of Undetermined malignant potential (STUMP) is a rare category of the prostate benign tumours, which has a variable clinical presentation, behavior and different approaches to manage it.

Case presentation

A 57 year-old male presented with voiding symptoms of the urinary tract and an increased PSA (14.7 ng/ml). Ultrasound and multiparametric MRI showed an enlarged prostate of 41 ml. Transurethral resection of the prostate (TURP) was performed with 11 g benign tissue removed. The patient presented one year later with the same symptoms; further ultrasound and parametric MRI demonstrated huge recurrence in the transition zone with a new prostate size of 131 ml.

Discussion

Despite no malignancy being identified in the initial TURP histology, the transition zone prostatic tumour behaved aggressively and recurred in just one year. For the first time in literature, the tumour recurred rapidly to three times the initial size and was removed using Holmium Laser enucleation of the prostate (HoLEP), after which no recurrence was seen in 11 months period.

Conclusion

HoLEP can be used to successfully enucleate STUMP tumours but the clinical behavior of the STUMP in prostate is still not understood well because of its rareness.

Mesenchymal tumors of the prostate

Mesenchymal tumors of the prostate are rare but often cause considerable diagnostic difficulty when encountered. These may be either benign or malignant and can arise within the prostate gland or in adjacent tissues. This review covers prostatic stromal proliferations (prostatic stromal tumor of uncertain malignant potential and stromal sarcoma), solitary fibrous tumor, myofibroblastic proliferations, smooth muscle neoplasms (leiomyoma and leiomyosarcoma), gastrointestinal stromal tumor, schwannoma, rhabdomyosarcoma, sarcomatoid carcinoma, postradiation sarcoma, and mixed epithelial stromal tumor of the seminal vesicle. Differential diagnostic considerations are emphasized, including descriptions of helpful histological and/or clinical clues and the use of adjuvant diagnostic techniques.

Targeting phenotypic heterogeneity in benign prostatic hyperplasia

Benign prostatic hyperplasia and associated lower urinary tract symptoms remain difficult to treat medically, resulting in hundreds of thousands of surgeries performed annually in elderly males. New therapies have not improved clinical outcomes since alpha blockers and 5 alpha reductase inhibitors were introduced in the 1990s. An underappreciated confounder to identifying novel targets is pathological heterogeneity. Individual patients display unique phenotypes, composed of distinct cell types. We have yet to develop a cellular or molecular understanding of these unique phenotypes, which has led to failure in developing targeted therapies for personalized medicine. This review covers the strategic experimental approach to unraveling the cellular pathogenesis of discrete BPH phenotypes and discusses how to incorporate these findings into the clinic to improve outcomes.

Metastatic prostatic stromal sarcoma: A challenging diagnosis on fine-needle aspiration with broad differential diagnosis

Prostatic stromal sarcomas (PSS) are rare solid organ mesenchymal sarcomas. PSS may pose difficult diagnostic challenges on fine needle aspiration biopsy. We report a 48-year-old man diagnosed with metastatic high grade prostatic stromal sarcoma by a CT-scan guided fine needle aspiration (FNA) biopsy of a right lower lung lobe nodule. We reviewed the literature on the epidemiologic, cyto-histological, and immunophenotypic findings and discussed the differential diagnosis for this rare entity.

Spectrum of Cystic Epithelial Tumors of the Prostate: Most Cystadenocarcinomas Are Ductal Type With Intracystic Papillary Pattern

Cystic epithelial tumors arising from the prostate are rare, and their full histologic spectrum has yet to be defined. Herein, we present 8 examples of prostatic cystic tumors including 1 giant multilocular cystadenoma and 7 cystadenocarcinomas. We divided the cystadenocarcinomas into "giant multilocular" cystadenocarcinoma (3) and "microscopic" cystadenocarcinoma (4) because of their differing clinical presentations with clinically apparent cystic masses in the former. The cystadenoma was an 11 cm multilocular cystic pelvic tumor in a 55-year-old man who presented with lower urinary tract symptoms. The cystadenoma was lined predominantly by benign acinar cells and had a distinct basal cell layer. No recurrence occurred 3 months after resection. The 3 patients with giant multilocular cystadenocarcinomas were 62 to 82 years old, had large pelvic cystic masses (up to 16 cm), and 2 presented with obstructive urinary and lower intestinal tract symptoms. One giant multilocular cystadenocarcinoma had a markedly high cystic fluid prostate-specific antigen at >80,000 ng/mL. All 3 giant multilocular cystadenocarcinomas were ductal adenocarcinoma with exuberant intracystic papillary formations. One tumor was associated with a high-grade noncystic conventional (acinar) adenocarcinoma (Gleason score 9 [ISUP grade group 5]). Follow-up on the 3 giant multilocular cystadenocarcinoma cases (7 to 21 mo) showed multiple metastases in 1 patient but was attributed to the high-grade conventional adenocarcinoma component. In addition, we described 4 examples of microscopic cystadenocarcinomas that were small (≤1 cm) solitary or multiple cystic tumors identified on pathologic examination of the prostate. In 3 of 4 microscopic cystadenocarcinomas the lining was ductal adenocarcinoma with occasional to exuberant papillae and appeared similar to the smaller cysts in the giant multilocular cystadenocarcinomas. One of the 4 microscopic cystadenocarcinomas had an acinar adenocarcinoma lining with occasional papillae and was associated with a conventional adenocarcinoma. Follow-up of the 4 patients with microscopic cystadenocarcinoma (1 to 14 mo) showed no evidence of disease. Review of literature highlighted similarities between the findings in our cases and previously published prostatic cystadenocarcinomas, including the markedly high cystic fluid prostate-specific antigen level in giant multilocular cystadenocarcinomas and the typical ductal adenocarcinoma morphology with intracystic papillary pattern. In conclusion, cystic epithelial tumors of the prostate exhibit unique clinicopathologic features. Cystadenocarcinomas, whether the clinically apparent giant multilocular form or the incidentally identified microscopic type, represent a rare underrecognized pattern of prostatic adenocarcinoma mostly within the histologic spectrum of the ductal variant.

Beyond Prostate Adenocarcinoma: Expanding the Differential Diagnosis in Prostate Pathologic Conditions

Recent advances in magnetic resonance (MR) imaging of the prostate gland have dramatically improved the ability to detect and stage adenocarcinoma of the prostate, one of the most frequently diagnosed cancers in men and one of the most frequently diagnosed pathologic conditions of the prostate gland. A wide variety of nonadenocarcinoma diseases can also be seen with MR imaging, ranging from benign to malignant diseases, as well as infectious and inflammatory manifestations. Many of these diseases have distinctive imaging features that allow differentiation from prostate acinar adenocarcinoma. Early recognition of these entities produces a more accurate differential diagnosis and may enable more expeditious clinical workup. Benign neoplasms of the prostate include plexiform neurofibroma and cystadenoma, both of which demonstrate distinctive imaging features. Stromal neoplasms of uncertain malignant potential are rare tumors of uncertain malignant potential that are often difficult to distinguish at imaging from more-malignant prostate sarcomas. Other malignant neoplasms of the prostate include urothelial carcinoma, primary prostatic carcinoid, carcinosarcoma, endometrioid or ductal adenocarcinoma, and mucinous adenocarcinoma. Prostatic infections can lead to abscesses of pyogenic, tuberculous, or fungal origins. Finally, miscellaneous idiopathic disorders of the prostate include amyloidosis, exophytic benign prostatic hyperplasia, and various congenital cysts. Considerable overlap can exist in the clinical history and imaging findings associated with these prostate pathologic conditions, and biopsy is often required for ultimate confirmation of the diagnosis. However, many diagnoses, including cystadenoma, mucinous adenocarcinoma, sarcoma, and abscesses, have distinct imaging features, which can enable the informed radiologist to identify the diagnosis and recommend appropriate clinical workup and management. (©)RSNA, 2016.