Intraprostatic fat: does it exist?

Incidence and Pitfalls of Adipose Tissue Encountered in Prostatic Transurethral Resections and Related Specimens

While the presence of adipose tissue and its involvement by prostatic cancer (extraprostatic extension) is well-recognized in prostate biopsies, adipose tissue in transurethral resections of the prostate (TURP) is largely unexplored. Herein, 200 consecutive TURPs and related specimens were reviewed, including a separate 3-year analysis of specimens containing prostatic cancer, with the following data collected: presence of fat, presence of cancer within fat, and quantity of fat. For specimens with both fat and prostatic cancer, specimen weight and tumor volume were recorded. Within the 200 consecutive TURPs and related specimens, adipose tissue was identified in 20%; 55% had 2.5 mm of adipose tissue; the number of fragments with adipose tissue ranged from 1 to 14. No correlation between specimen weight and measured extent of adipose tissue or number of fragments with adipose tissue was identified. Of all the specimens with prostatic cancer, 15/56 (27%) involved adipose tissue, with two specimens with large cancer volume (>90%) demonstrating extensive involvement of adipose tissue. Adipose tissue is frequently present within TURP and related specimens with variability in extent. The etiology behind encountering adipose tissue is uncertain, and it could represent resection into peri-prostatic fat, intraprostatic fat, or bladder neck fat sampling. Although encountering adipose tissue involved by cancer in TURP and related specimens may imply extraprostatic extension (pT3a), further studies are needed to corroborate these findings as well as to determine if these should be included in reported synoptics.

Obesity-Related Cross-Talk between Prostate Cancer and Peripheral Fat: Potential Role of Exosomes

The molecular mechanisms of obesity-induced cancer progression have been extensively explored because of the significant increase in obesity and obesity-related diseases worldwide. Studies have shown that obesity is associated with certain features of prostate cancer. In particular, bioactive factors released from periprostatic adipose tissues mediate the bidirectional communication between periprostatic adipose tissue and prostate cancer. Moreover, recent studies have shown that extracellular vesicles have a role in the relationship between tumor peripheral adipose tissue and cancer progression. Therefore, it is necessary to investigate the feedback mechanisms between prostate cancer and periglandular adipose and the role of exosomes as mediators of signal exchange to understand obesity as a risk factor for prostate cancer. This review summarizes the two-way communication between prostate cancer and periglandular adipose and discusses the potential role of exosomes as a cross-talk and the prospect of using adipose tissue as a means to obtain exosomes in vitro. Therefore, this review may provide new directions for the treatment of obesity to suppress prostate cancer.

Prostate cancer reporting and staging: needle biopsy and radical prostatectomy specimens

Prostatic adenocarcinoma remains the most common cancer affecting men. A substantial majority of patients have the diagnosis made on thin needle biopsies, most often in the absence of a palpable abnormality. Treatment choices ranging from surveillance to radical prostatectomy or radiation therapy are largely driven by the pathologic findings in the biopsy specimen. The first part of this review focuses on important morphologic parameters in needle biopsy specimens that are not covered in the accompanying articles. This includes tumor quantification as well as other parameters such a extraprostatic extension, seminal vesicle invasion, perineural invasion, and lymphovascular invasion. For those men who undergo radical prostatectomy, pathologic stage and other parameters are critical in prognostication and in determining the appropriateness of adjuvant therapy. Staging parameters, including extraprostatic extension, seminal vesicle invasion, and lymph node status are discussed here. Surgical margin status is also an important parameter and definitions and reporting of this feature are detailed. Throughout the article the current reporting guidelines published by the College of American Pathologists and the International Collaboration on Cancer Reporting are highlighted.

Intraprostatic adipose tissue: a study of 427 whole mount radical prostatectomy specimens

Prostatic adenocarcinoma is the most frequently diagnosed cancer in American men. Tumor Gleason grade and stage provide extremely valuable prognostic information and play an important role in therapeutic decision making and patient counseling. A biopsy or radical prostatectomy specimen revealing carcinoma extending into extraprostatic tissue permits a T3 classification. This is most easily recognized, particularly in a needle biopsy, when tumor is seen to invade the adipose tissue. The existence of intraprostatic adipose tissue is somewhat controversial. To investigate this, formalin-fixed paraffin-embedded whole-mount radical prostatectomy specimens from 427 patients with adenocarcinoma were evaluated for intraprostatic adipose tissue. It was defined as any collection of adipocytes amid or internal to the most peripheral glands. The amount, anatomic location, and relationship to normal structures were also recorded. Intraprostatic adipose tissue was identified in 17 (3.98%) of cases. It consisted of small microscopic foci composed of 5 to 20 adipocytes. In 13 cases, the fat was intimately associated with benign glands. In another 2 cases, it was associated with small nerves, and in 2 cases was random with no specific localization. Intraprostatic adipose tissue was located in the peripheral zone in 15 cases and in the central zone in 2. Intraprostatic adipose tissue, although uncommon, does exist. Therefore, caution must be exercised in diagnosing extraprostatic extension based only upon identification of fat invasion, especially in a needle biopsy. The small size of foci of adipose tissue and its admixture with benign glands are useful morphologic clues in distinguishing it from extraprostatic fat.

Interobserver variability between expert urologic pathologists for extraprostatic extension and surgical margin status in radical prostatectomy specimens

Accurate Gleason score, pathologic stage, and surgical margin (SM) information is critical for the planning of post-radical prostatectomy management in patients with prostate cancer. Although interobserver variability for Gleason score among urologic pathologists has been well documented, such data for pathologic stage and SM assessment are limited. We report the first study to address interobserver variability in a group of expert pathologists concerning extraprostatic soft tissue (EPE) and SM interpretation for radical prostatectomy specimens. A panel of 3 urologic pathologists selected 6 groups of 10 slides designated as being positive, negative, or equivocal for either EPE or SM based on unanimous agreement. Twelve expert urologic pathologists, who were blinded to the panel diagnoses, reviewed 40x whole-slide scans and provided diagnoses for EPE and SM on each slide. On the basis of panel diagnoses, as the gold standard, specificity, sensitivity, and accuracy values were high for both EPE (87.5%, 95.0%, and 91.2%) and SM (97.5%, 83.3%, and 90.4%). Overall kappa values for all 60 slides were 0.74 for SM and 0.63 for EPE. The kappa values were higher for slides with definitive gold standard EPE (kappa=0.81) and SM (kappa=0.73) diagnoses when compared with the EPE (kappa=0.29) and SM (kappa=0.62) equivocal slides. This difference was markedly pronounced for EPE. Urologic pathologists show good to excellent agreement when evaluating EPE and SM. Interobserver variability for EPE and SM interpretation was principally related to the lack of a clearly definable prostatic capsule and crush/thermal artifact along the edge of the gland, respectively.

Invasion of fat justifies assignment of stage pT3a in prostatic adenocarcinoma

AIMS

The detection of invasive cancer cells within the adipose tissue of needle biopsies has been regarded as bona fide evidence of extraprostatic tumour extension, and as a consequence may influence subsequent patient management. However, the identification of rare intraprostatic fat from recent reports involving series of autopsies has challenged this practice principle. We examined totally embedded, whole-mounted radical prostatectomy specimens in order to determine the occurrence of intraprostatic fat in prostatic tissue, and further, to assess the importance of the identification of fat infiltration by neoplastic cells in needle biopsy specimens as a marker of extraprostatic infiltration by tumour.

METHODS

Between 2000 and 2003, 313 consecutive patients underwent radical prostatectomy for clinically localised prostate cancer in the Indiana University Hospital. All radical prostatectomy specimens were completely embedded and whole mounted for histological examination. All slides were reviewed and evaluated for the presence or absence of intraprostatic fat. Other pathological characteristics of prostate cancer were also assessed and clinical data were gathered by a review of patient charts.

RESULTS

The mean age of patients was 60 years. None of these 313 radical prostatectomy specimens revealed any adipose tissue components within the most peripheral boundary of normal prostatic acini in the prostate.

CONCLUSIONS

We found no evidence of intraprostatic fat and our findings suggest that, at best, the occurrence of fat within the prostate is of extreme rarity. Accordingly, the finding of carcinoma invading adipose tissue in needle biopsies should continue to be considered as extraprostatic extension and stage pT3a assigned.