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

Solitary fibrous tumor of the prostate with accompanying low-grade prostate cancer

We present the rare case of a 51-year-old male diagnosed with a solitary fibrous tumor (SFT) of the prostate, along with a concurrent low-grade prostate adenocarcinoma (Gleason score 3 + 3, Grade Group 1). The diagnosis was confirmed by positive immunohistochemical markers, including CD34, BCL2, and STAT6, and molecular analysis showing a NAB2-STAT6 fusion. Following successful surgical management and the simultaneous diagnosis of a pulmonary relapse from a prior thyroid carcinoma, the patient remains under clinical surveillance. This is particularly significant given the patient's history of multiple tumors, including Hodgkin's lymphoma, papillary thyroid carcinoma, prostate cancer, and SFT.

Solitary fibrous tumours involving the genitourinary tract: a case series in rare locations, highlighting the role of STAT6 immunohistochemistry

Solitary fibrous tumour (SFT) is a mesenchymal neoplasm with variable behaviour, very rarely involving the genitourinary (GU) tract. Most reported cases correspond to isolated case reports. STAT6 immunohistochemistry is a more recent and reliable diagnostic marker. The pathology database of two tertiary institutes was searched for SFTs involving the GU tract. STAT6 strong diffuse nuclear staining confirmed the diagnosis in all four cases, and the NAB2::STAT6 fusion was demonstrated by NGS in one case. Two cases were diagnosed in needle biopsy, one involving the prostate and the other involving the seminal vesicle. One case corresponded to a pelvic mass inseparable from and infiltrating the prostate and bladder. The remainder represented an exceedingly rare involvement of the spermatic cord. Involvement by a SFT should be considered in the differential diagnosis of spindle cell lesions involving GU organs. STAT6 strong diffuse nuclear staining is an important ancillary tool, particularly in a biopsy.

Solitary fibrous tumors in prostate: a case report with review of the literature

BACKGROUND

Solitary fibrous tumor (SFT) is a relatively rare type of mesenchymal neoplasm that occurs most frequently in the pleura. However, SFT originating from the prostate is particularly uncommon and only approximately 39 cases were reported before. Herein, we reported a rare case of a patient diagnosed with prostate SFT and presented a literature review.Case presentation: A 50-year-old Asian with irritative urinary symptoms was admitted to our hospital and almost all the evidence indicated that benign prostate hyperplasia (BPH) caused his symptoms. Therefore, transurethral resection of the prostate (TURP) was performed, but histopathological and Immunohistochemical (IHC) assessments showed that spindle cells arranged disorderly in the TURP specimen with a cluster of differentiation 34 (CD34), B-cell lymphoma-2 (Bcl-2), and signal transducer and activator of transcription 6 (STAT6) highly expressed and SFT was diagnosed. Finally, the patient underwent a radical prostatectomy and there was no disease progression observed thereafter.

CONCLUSIONS

Prostate SFT is extremely rare, and to our knowledge, this is the first case of prostate SFT that is difficult to differentiate from small volume BPH. IHC examinations are of great diagnostic value. Radical resection of the tumor appears to be the most effective method at present and continuous follow-up is highly recommended.

Angiomyofibroblastoma and Potential Mimicking Soft Tissue Tumors That May Occasionally Present in the Retroperitoneum: An Approach to the Differential Diagnosis With Report of an Unusual Index Case Abutting the Kidney

The retroperitoneal soft tissues, extending from the pelvic floor to the level of the diaphragm, are the source of a variety of mesenchymal neoplasms with overlapping features and distinct clinical behaviors, making their distinction of crucial importance. Herein, we report a rare retroperitoneal angiomyofibroblastoma (AMFB) that presented as a right abdominal mass in a 25-year-old woman and that clinically simulated a primary renal carcinoma. The patient underwent complete surgical resection showing a well-circumscribed tumor adjacent to but separate from the right kidney. It was comprised of irregular, often anastomosing islands and cords of plump to spindled cells in a collagenous stroma with numerous thin-walled vessels. The tumor cells clustered around the vessels and admixed with moderate numbers of adipocytes. There was neither significant nuclear atypia nor mitotic activity. Immunohistochemically, the tumor cells showed strong reactivity for desmin, diffuse expression of estrogen and progesterone receptors, retained nuclear expression of retinoblastoma protein, and absent CD34 expression. The immunomorphological features were these of a "lipomatous variant" of AMFB of the retroperitoneum. The occurrence of AMFB in the retroperitoneum is unexpected since it mostly develops in the lower genital tract of young women, making its recognition in this rare location difficult. As a consequence, more common pelvic or retroperitoneal soft tissue neoplasms may represent the primary diagnostic considerations. We, therefore, review a variety of soft tissue tumors occurring in the pelvis/retroperitoneum that, to some degree, may mimic AMFB, and present key findings to assist in accurate diagnosis.

Solitary Fibrous Tumor of the Prostate: A Case Report and Literature Review

Solitary fibrous tumors (SFTs) usually occur in the pleura and account for two-thirds of all cases; however, SFTs occurring in the prostate are extremely rare. Approximately 25 cases have been reported in the literature to date. This study reports the case of a 43-year-old man referred to our hospital with the chief complaint of a pelvic tumor after careful examination. The tumor marker levels were within normal limits. T2-weighted magnetic resonance imaging revealed a tumor, demonstrating primarily low signal intensity. It showed a capsule-like rim at the left lobe of the prostate, suggesting that the tumor was partially invading the rectal wall. Histopathological examination of needle-core biopsies showed spindle cell neoplasm with small and fusiform cells, strongly expressing signal transducer and activator of transcription 6 (STAT6) with a ramifying vascular network. Therefore, the clinical diagnosis of the patient was SFT of the prostate and robot-assisted radical prostatectomy was performed. Histopathological examination revealed that the tumor was composed of spindle cells with patternless and staghorn patterns. Immunohistochemical analysis showed a strong expression of STAT6. Furthermore, the tumor was partially positive for CD34. Therefore, the patient was diagnosed with SFT of the prostate. Two years after the initial diagnosis, the patient was alive with normal erectile function, continence status, and no evidence of the disease.

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.

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.