One of the most powerful prognostic predictors in prostate cancer is Gleason grading system. This system more accurately reflects prostate cancer biology. Nevertheless it has its own deficiencies that can potentially impact patient care.
Prostate cancer has different histologic patterns. For ease of grading only the five prognostic patterns were demonstrated by Dr Gleason.
Gleason pattern 1
Gleason pattern 2
Gleason pattern 3 - consists of well-formed, individual glands of various sizes including branching glands. The glands should form discrete units, such that one could draw a circle around each individual gland. The glands should not be fused with one another.
Gleason pattern 4 - includes poorly-formed, fused and cribriform glands. The glands are dilated containing intraluminal cribriform structures with a single point of attachment resembling renal glomerulus. Studies have shown that cribriform pattern in radical prostatectomy specimens are associated with biochemical recurrence, extraprostatic extension, positive surgical margins distant metastasis and cancer-specific mortality. For these reason all cribriform glands should be assigned Gleason pattern 4.
Gleason pattern 5 - consists of sheets of tumors, individual cells and cords of cells.
Intraductal carcinoma (IDC) - it is the spread of adenocarcinoma within prostatic ducts. It is also considered to be the extension of high grade invasive tumor into the prostatic ducts. Detection of IDC has been associated with high grade tumor and high stage disease and the decreased cancer-free survival rate. In addition, IDC is an independent prognosticator of early biochemical recurrence and metastases in patients treated with radiation therapy.
However, IDC is occasionally a precursor lesion, rather than extension of the invasive tumor into the ducts and may be present at radical prostatectomy either without invasive carcinoma or with Gleason score 3 + 3 = 6 cancer.
Mucinous adenocarcinoma is a variant of prostatic adenocarcinoma where the infiltrative glands have abundant extracellular mucin. (That is why there is no restricted diffusion??). This histologic variant must be graded based on its underlying growth pattern.
Grade on needle core biopsy
Standard of care for urologists is to perform a 10-12 prostatic core biopsy. In some cases, multiple cores may be positive for cancer, with different cores having a different Gleason grade.
As long as the cores are submitted in separate containers or designated by location (for example by ink) the pathologist should report the grades of each core separately.