Nonepithelial Tumors and Tumor-Like Lesions of the Prostate Gland

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.

[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.

Prostate Benign Diseases

Magnetic resonance imaging (MRI) has been increasingly used in the detection, localization, and staging of prostate cancer. Because of its excellent soft tissue contrast and multiplane imaging, it can be also very useful in the evaluation of benign prostate diseases. Prostatic benign disorders have a high prevalence, vastly represented by benign prostatic hyperplasia and prostatitis. On the contrary, benign prostatic neoplasms are extremely rare, represented by multilocular cystadenoma, leiomyomas, hemangioma, and granular cell tumor, although these uncommon tumors have been most encountered due to widespread use of MRI. Congenital prostatic anomalies are associated with defects in the development of the prostate embryology, including hypoplasia, ectopia, and vascular malformations, abnormalities rarely seen on cross-sectional imaging. Prostatic cysts are the most common development abnormalities and occasionally are related to clinical symptoms, mainly due to infection and hemorrhage. As with prostate cancer, multiparametric MRI is a reliable tool for the diagnosis and management of benign prostatic diseases as well, providing additional information such morphological changes of the prostate, more accurate prostatic measurements, and functional characteristics of nonmalignant prostatic lesions. In this review, we discuss MRI findings of these benign prostatic diseases.

Imatinib Spares cKit-Expressing Prostate Neuroendocrine Tumors, whereas Kills Seminal Vesicle Epithelial-Stromal Tumors by Targeting PDGFR-β

Prostate cancer is a leading cause of cancer-related death in males worldwide. Indeed, advanced and metastatic disease characterized by androgen resistance and often associated with neuroendocrine (NE) differentiation remains incurable. Using the spontaneous prostate cancer TRAMP model, we have shown that mast cells (MCs) support in vivo the growth of prostate adenocarcinoma, whereas their genetic or pharmacologic targeting favors prostate NE cancer arousal. Aiming at simultaneously targeting prostate NE tumor cells and MCs, both expressing the cKit tyrosine kinase receptor, we have tested the therapeutic effect of imatinib in TRAMP mice. Imatinib-treated TRAMP mice experience a partial benefit against prostate adenocarcinoma, because of inhibition of supportive MCs. However, they show an unexpected outgrowth of prostate NE tumors, likely because of defective signaling pathway downstream of cKit receptor. Also unexpected but very effective was the inhibition of epithelial-stromal tumors of the seminal vesicles achieved by imatinib treatment. These tumors normally arise in the seminal vesicles of TRAMP mice, independently of the degree of prostatic glandular lesions, and resemble phyllodes tumors found in human prostate and seminal vesicles, and in breast. In both mice and in patients, these tumors are negative for cKit but express PDGFR-β, another tyrosine kinase receptor specifically inhibited by imatinib. Our results imply a possible detrimental effect of imatinib in prostate cancer patients but suggest a promising therapeutic application of imatinib in the treatment of recurrent or metastatic phyllodes tumors. Mol Cancer Ther; 16(2); 365-75. ©2016 AACR.

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.

A prostate fibromyxoid sarcoma with smooth muscle differentiation in a F344xBNF1 rat

This report describes a spontaneous prostate fibromyxoid sarcoma with smooth muscle differentiation in an approximately 136-week-old intact male F344xBNF1 rat on a diet study for 2 weeks. At necropsy, the prostate was markedly distorted and enlarged by a firm white multinodular mass (6.0 × 4.5 × 3.5 cm). Histopathologically, the mass consisted of solid sheets of interlacing mesenchymal spindle cells with indistinct cell borders. Nuclei were separated by variable amounts of hyaline to fibrillar eosinophilic and/or myxomatous material. The extracellular myxomatous material tended to form whorls and stained positively with alcian blue. The mass stained strongly with Masson trichrome and vimentin throughout. Approximately 5% of the neoplastic cells were positive for smooth muscle actin, and none stained for desmin and pancytokeratin. To the authors' knowledge, this fibromyxoid sarcoma with smooth muscle differentiation is the first such described prostatic sarcoma in a rat.

Unusual features of gastrointestinal stromal tumor on PET/CT and CT imaging

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. It can be benign or malignant in behavior. Stomach, being the most common site (70%) for GISTs, is followed by the small intestine (20%). Anorectal, colonic, and esophageal GISTs are uncommon, whereas extraintestinal GISTs are extremely rare. The presenting symptoms are highly dependent on tumor size and location, although a large number of GISTs are asymptomatic. The purpose of this article is to highlight the unusual characteristics of GISTs illustrated by PET/CT and CT imaging. These characteristics are organized into (1) unusual tumor location, (2) unusual clinical presentation, and (3) unusual sites of metastasis. Knowing the uncommon features of GISTs is important, as they are more often seen nowadays with the increasingly important role of PET/CT and CT in GIST management; and these tumors are associated with a poorer prognosis and unwanted delay in diagnosis is avoidable. With the availability of effective treatment by imatinib mesylate, a prompt and early diagnosis is essential for disease control. All GISTs illustrated in this article are pathologically proven.

Hemangioma of the prostate--an unusual cause of lower urinary tract symptoms: case report

Background

Hemangioma of the prostate gland is extremely rare and only a few cases have been reported. There have been several cases of hemangioma of posterior urethra, urinary bladder and periprostatic plexus in the literature, all presenting with hematuria or hematospermia. Diagnosis of prostatic hemangioma is difficult due to its rarity and unspecific symptoms such as hematuria, hematospermia or lower urinary tract symptoms. It cannot be detected by conventional examinations such as cystoscopy or standard rectal ultrasonography.

Case presentation

We present a case of prostatic hemangioma in an 84-year old male presenting with lower urinary tract symptoms. Bleeding has not been a feature in our case and diagnosis was not made until after operation. The patient was treated as a case of bladder neck outflow obstruction with transurethral resection of prostate gland and simultaneous bladder neck incisions. A period of self-catheterization was instituted due to postoperative urinary retention as the result of detrusor insufficiency.

Conclusion

Hemangioma of prostate gland is extremely rare and symptomatic prostatic hemangioma should be treated either by transurethral resection of prostate or laser evaporation.

Malignancy arising in seminal vesicles in the transgenic adenocarcinoma of mouse prostate (TRAMP) model

BACKGROUND

Transgenic adenocarcinoma of mouse prostate (TRAMP) mice, derived by prostate specific expression of SV40 large T antigen using the rat probasin promoter, all develop prostate tumors akin to human prostate cancers. More recently, epithelial-stromal (ES) tumors resembling phyllodes tumors have been described in the seminal vesicles of TRAMP mice. We report malignancy arising in these ES tumors of the seminal vesicles in TRAMP mice.

METHODS

H&E stained sections from 28-week-old TRAMP mice autopsies were examined. Immunostains (cytokeratin, vimentin, desmin, and MIB-1) and electron microscopy were performed on selected blocks of the genitourinary system and metastatic tumor nodules.

RESULTS

The seminal vesicles frequently develop tumors containing broad papillae, with bland epithelium and a cellular spindled stroma just beneath the epithelium. The stromal cells have high nuclear to cytoplasmic ratio, frequent apoptotic cells and mitoses. In some cases, the stromal cells become large mass lesions that overgrow the prostate. The epithelium can also proliferate and become malignant. The tumors have high proliferation indices by MIB-1. Some metastatic tumors have characteristics similar to the seminal vesicle ES tumor.

CONCLUSIONS

Metastatic tumors in TRAMP mice show three patterns: (1) A definite adenocarcinoma pattern metastatic from the prostate; (2) poorly differentiated tumor without epithelial differentiation; (3) carcinosarcomatous pattern. The carcinosarcomatous pattern and some of the poorly differentiated tumors likely arise from seminal vesicle ES tumors.

Primary prostatic haemangiosarcoma causing severe haematuria in a dog

A 10-year-old, entire, male, mixed-breed dog was presented for severe haematuria and stranguria. Ultrasound revealed a large intraluminal urinary bladder blood clot and a prostatic space-occupying lesion. Invasion of the lesion into the prostatic urethra was detected ultrasonographically during compression of the urinary bladder. Post-mortem examination revealed primary prostatic haemangiosarcoma infiltrating the urethra. Haemangiosarcoma should be considered as a rare cause of prostatic mass lesions, haematuria or lower urinary tract signs in dogs.