Digital quantification of five high-grade prostate cancer patterns, including the cribriform pattern, and their association with adverse outcome

Do adenocarcinomas of the prostate with Gleason score (GS) ≤6 have the potential to metastasize to lymph nodes?

Although rare, there are cases within reported series of men with Gleason score (GS) ≤6 on radical prostatectomies that show pelvic lymph node (LN) metastases. However, there are no studies on whether pelvic LN metastases occur in tumors with GS ≤6 using the International Society of Urological Pathology (ISUP) updated GS system. We performed a search of the radical prostatectomy databases at 4 large academic centers for cases of GS ≤6. Only prostatectomies submitted and embedded in entirety with pelvic LN dissections were included. A combined total of 14,123 cases were identified, of which 22 cases had a positive LN. Histopathologic review of 19 cases (3 cases unavailable for review) showed higher grade than originally reported by the pathologists in all cases. Of the 17 pre-ISUP reviewed cases, 2 were upgraded to 4+3=7 with both cribriform and poorly formed glands. One case was upgraded to 4+3=7 with tertiary pattern 5 displaying cribriform glands, poorly formed glands, and cords of single cells. Eleven cases were upgraded to 3+4=7 with glomeruloid structures and small to large cribriform glands (1 of these also had features of ductal adenocarcinoma). Two cases had tertiary pattern 4 with small cribriform glands. One case had a prominent colloid component that would currently be graded as 4+5=9 because of large cribriform glands and solid sheets of cells within the mucin. Of the 2 post-ISUP cases, 1 demonstrated tertiary pattern 4, and the other showed GS 3+4=7 with irregular cribriform glands. Undergrading is the primary reason for LN positivity with GS ≤6, which has decreased significantly since the adoption of the ISUP grading system in 2005. Of over 14,000 totally embedded radical prostatectomies from multiple institutions, there was not a single case of a GS ≤6 tumor with LN metastases. In contrast to prevailing assumptions, GS ≤6 tumors do not appear to metastasize to LNs. Rather, Gleason pattern 4 or 5, as better defined by the current ISUP updated grading system, is required for metastatic disease.

Gleason grading: past, present and future

In 1966 Donald Gleason developed his grading and scoring system for prostatic adenocarcinoma. This classification was refined in 1974 and gained almost universal acceptance, being classified as a category 1 prognostic parameter by the College of American Pathologists. Modifications to the classification were recommended at a conference convened by the International Society of Urological Pathology (ISUP) in 2005. This modified classification has resulted in a significant upgrading of tumours, although some studies have shown a greater concordance between needle biopsy and radical prostatectomy scores when compared to classical Gleason (CG) grading. The ISUP consensus conference recommended that for needle biopsies higher tertiary patterns should be incorporated into the final Gleason score, and this has been correlated with biochemical failure, tumour volume and mortality. Recently the validity of including cribriform glands as a component of Gleason pattern 3 has been questioned and it has been recommended that all tumours showing cribriform architecture should be classified as Gleason pattern 4. The recommendations arising from the 2005 Consensus Conference were largely unsupported by validating data, yet this new grading system has achieved widespread usage. It is unfortunate that recent suggestions for further modification are similarly lacking in supporting evidence. In view of this it is recommended that the Modified Gleason Scoring Classification should continue to be utilized in its original (2005) format and that any future alterations should be implemented only when mandated by tumour-related outcome studies.

Usual and unusual histologic patterns of high Gleason score 8 to 10 adenocarcinoma of the prostate in needle biopsy tissue

High Gleason score 8 to 10 adenocarcinoma is the most aggressive and potentially lethal form of prostate cancer. The 2005 International Society of Urological Pathology (ISUP)-modified Gleason grading scheme defines several gland arrangements of high Gleason grade patterns 4 and 5. The aim of this investigation was to quantitate the frequency of the ISUP-defined high Gleason grade patterns in needle biopsy tissue, to determine the common admixtures and to characterize patterns not presented in the 2005 ISUP report. For patients who underwent radical prostatectomy, we analyzed for association of specific high-grade patterns in needle biopsy with extraprostatic extension in radical prostatectomy tissues. A total of 268 prostate needle biopsy cases with Gleason score of 8 to 10 were examined. A mean of 3.6 patterns (range, 1 to 8) were identified per case and only 12% of cases had a pure single pattern. Ill-defined glands with poorly formed lumina (at 57%) and fused microacinar glands (at 53%) comprised the predominant and most frequently admixed patterns. Single cells and single signet ring cells were present in 53% and 31% of cases, respectively. Additional patterns in order of frequency included cords (35%), cribriform glands (25%), sheets of cells (19%), chains (4%), glomeruloid (3%), comedonecrosis (2%), and hypernephromatoid (1 case=0.3%). Gleason score 8 to 10 carcinomas are typically extensive in needle core tissue, with a mean of 4.4 positive cores (range, 1 to 15 cores) per case. Only 14 cases (5%) had high-grade minimal carcinoma measuring <1 mm in needle core tissue. Gleason grade patterns not described in the 2005 ISUP report include single file growth, solid cylinders, and nested patterns. The single file pattern was present in 40% of cases, and the small solid nested pattern was detected in 24% of cases. One case displayed solid cylinders. Only the single file pattern was associated with extraprostatic extension at radical prostatectomy (P=0.005). These results show that the 2005 ISUP-defined patterns of high Gleason score 8 to 10 prostatic adenocarcinoma can be stratified on the basis of frequency of occurrence in needle biopsy tissue. Three patterns not defined in the 2005 ISUP scheme have been characterized, including single file, nested, and solid cylinder arrangements. As aggressive and potentially lethal prostate cancer is most often of Gleason score 8 to 10, it is important for diagnostic recognition purposes to be aware of the frequency of various patterns encountered in high Gleason score 8 to 10 adenocarcinomas, the types of pattern admixtures, and the histomorphologic presentation of unusual patterns. We propose that Gleason grade assignments should incorporate single file, solid nested, and solid cylinder arrangements as high-grade pattern 5 because of the absence of glandular luminal space formation.

Current perspectives on Gleason grading of prostate cancer

The 5-tier Gleason grading system for prostate cancer, introduced in 1966, has been proven to be one of the main independent predictors of prostate cancer outcome. This review addresses interobserver concordance in Gleason grading; the persistence of grading discrepancies with frequent upgrading from the biopsy to the prostatectomy specimen; the 2005 International Society of Urologic Pathologists' modifications to Gleason grading; the impact of this modified grading on grade migration and outcome prediction; and molecular correlates of cancer morphology. Data from the most recent years are emphasized.

Pseudolumen size and perimeter in prostate cancer: correlation with patient outcome

We demonstrated in 2011 that 61% of men with postoperative PSA failure had some cribriform pattern of prostate cancer, versus 16% of nonfailures (OR = 5.89, P < .0001). That study used digitized radical prostatectomy slides from 153 men, 76 failures (≥0.2 ng/mL) matched to 77 nonfailures. The current study's hypothesis: pseudolumen size and shape variability could stratify outcome within histologic patterns (single separate acini, separate acini with undulating lumens, fused small acini, papillary, cribriform). Pseudolumens were filled digitally on image captures from previously annotated specimens. Among all 5 patterns, pseudolumen spaces averaged smaller in failures than nonfailures. After multivariate analysis controlling for stage, age, margin, cancer amount, prostate volume, and presence of individual cells (grade 5), this retained significance only for the undulating-lumens and papillary patterns. In undulating-lumens pattern, PSA failures had smaller mean pseudolumen space sizes (P = .03) but larger perimeters (P = .04), implying more pseudolumen irregularity. In papillary pattern, the number of pseudolumen spaces was higher in failures (P = .015), space size was smaller (P = .11), perimeters were smaller (P = .04), and perimeter/size ratio was higher (P = .02). In conclusion, digitally measured pseudolumen size and shape may associate with outcome.