Grading of prostate cancer: a work in progress

Abstract

Grading of prostate cancer has evolved substantially over time, not least because of major changes in diagnostic approach and concomitant shifts from late‐ to early‐stage detection since the adoption of PSA testing from the late 1980s. After the conception of the architecture‐based nine‐tier Gleason grading system more than 50 years ago, several changes were made in order to increase its prognostic impact, to reduce interobserver variation and to improve concordance between prostate needle biopsy and radical prostatectomy grading. This eventually resulted in the current five‐tier grading system, with a much more detailed description of the individual architectural patterns constituting the remaining three Gleason patterns (i.e. grades 3–5). Nevertheless, there is room for improvement. For instance, distinction of common grade 4 subpatterns such as ill‐formed and fused glands from the grade 3 pattern is challenging, blurring the division between low‐risk patients who could be eligible for deferred therapy and those who need curative therapy. The last few years have witnessed the publication of several studies on the prognostic impact of individual architectural subpatterns showing that, in particular, the cribriform pattern exceeded the prognostic impact of other grade 4 subpatterns. This review provides an overview of the changes in prostate cancer grading over time and provides a thorough description of the various Gleason subpatterns, the current evidence of their prognostic impact and areas of contention. Potential practical ways for improvements of the current grading system are also put forward.

Histopathological Features of MRI‐Invisible Regions of Prostate Cancer Lesions

“…Of the visible lesions, some regions were not visible, which will result in underestimation of tumor volume. The invisible regions have different histopathology characteristics than visible regions, confirming previous results that a prostate lesion consists of a combination of multiple subpatterns that represent themselves differently on mpMRI . Bratan et al also looked at density as an influencing factor for the accuracy of volume assessment: from their analysis the Gleason score, size, and Likert score were significant predictors for accurate volume assessment .…”

“…A GP 4 region was classified as having cribriform growth if a part consisted of expansile rounded tumor areas with a cribriform pattern, large‐sized glands with glomeruloid features showing a cribriform pattern, or complex fused glands with irregular cribriform areas (Fig. b) . In addition to the subpatterns classification suggested by Kweldam et al, a lesion or a region was classified as having homogeneous morphology when the morphology of all tumor cells was the same, and heterogeneous morphology when more than one type of morphology was present; for instance, if both acinar and foamy tumor cells were present (Fig.…”

“…b) . In addition to the subpatterns classification suggested by Kweldam et al, a lesion or a region was classified as having homogeneous morphology when the morphology of all tumor cells was the same, and heterogeneous morphology when more than one type of morphology was present; for instance, if both acinar and foamy tumor cells were present (Fig. c).…”

“…To be able to improve volume assessment of lesions with mpMRI, we first need to understand why parts of lesions are not visible. Based on histopathology a single lesion can consist of a combination of Gleason patterns (GPs) and even within a single GP multiple architectural subpatterns can be present . Langer et al indicated that there is a significant relation between histological features of normal and malignant prostate tissue and mpMRI parameters .…”

“…Based on histopathology a single lesion can consist of a combination of Gleason patterns (GPs) and even within a single GP multiple architectural subpatterns can be present. 14 Langer et al indicated that there is a significant relation between histological features of normal and malignant prostate tissue and mpMRI parameters. 15 Moreover, different Gleason subpatterns have different signal intensities on T 2 -weighted (T 2 W) images.…”