Quantified analysis of histological components and architectural patterns of gleason grades in apparent diffusion coefficient restricted areas upon diffusion weighted MRI for peripheral or transition zone cancer locations.

PURPOSE: To quantify and compare the histological components and architectural patterns of Gleason grades in cancerous areas with restriction on apparent diffusion coefficient (ADC) maps. MATERIALS AND METHODS: Twelve consecutive cases with 14 separate ADC restriction areas, positive for cancer in the peripheral zone (PZ) and transition zone (TZ) were included. All had 3 Tesla MRI and radical prostatectomy. Ten regions of interest (ROIs) within and outside the 14 ADC restriction areas positive for cancer were selected. For each ROI, we performed quantitative analysis of (a) prostate benign and malignant histological component surface ratios, including stroma, glands, epithelium, lumen, cellular nuclei; (b) percent of Gleason grades and measures of ADC values. Means of histological components according to ADC restriction for cancerous area were compared with analyses of variance with repeated measures. RESULTS: Independent predictors of the probability of cancer were median epithelium/ROI ratio (P = 0.001) and nuclei/ROI ratio (P = 0.03). Independent predictors of the probability of ADC restriction were malignant glands/ROI and luminal space/ROI (P < 0.0001). Effect of malignant glands/ROI area was different according to the localization of the ROI (P = 0.03). We observed an overall difference between the means for all of the histological components for the comparison of true positive and false negative (P < 0.0001), except for the percent of Gleason grade 4 (P = 0.18). In TZ cancers, a predominant grade 3 pattern was associated with low ADC values. In PZ cancers, a predominant grade 4 pattern was associated with low ADC values. CONCLUSION: Determinants of low ADC were high ratio of malignant glands/ROI area which may be seen in Gleason grades 3 or 4 cancers. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1786-1796.

Understanding the pathological implications of MRI: application to focal therapy planning.

PURPOSE OF REVIEW: The current challenge in prostate cancer (PCa) focal therapy indication and planning is how to accurately estimate tumor parameters such as volume, extent and grade. In addition to biopsy results, MRI provides an estimation of PCa contour, volume and histopathological characteristics such as presence of high Gleason grade. Among MRI sequences, diffusion-weighted imaging with apparent diffusion coefficient map is the sequence that showed the best results for cancer aggressiveness characterization. RECENT FINDINGS: It was shown that the higher the Gleason score, the lower the apparent diffusion coefficient value. However, accuracy is not sufficient for peripheral zone cancers to be validated for clinical decision and it was not enough investigated for transition zone cancers. Analysis of tumor extent showed a significant underestimation of tumor volume by imaging and this finding should be taken into consideration when planning focal therapy procedures. SUMMARY: Pathological implications of MRI for focal therapy planning are significant but not mature enough to be validated. Future research should aim to quantify cellularity and architectural patterns of PCa Gleason system in correlation with signal abnormalities for better assessment of tumor aggressiveness and extent, and to compare the boundaries of tumors between MRI and histopathological evaluation in order to define an optimal treatment margin.