Invasion of fat justifies assignment of stage pT3a in prostatic adenocarcinoma

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.

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.

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.

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.