HISTOLOGICAL GRADE HETEROGENEITY IN MULTIFOCAL PROSTATE-CANCER - BIOLOGICAL AND CLINICAL IMPLICATIONS

In order to understand the clinical and biological implications of pro state cancer multifocality and heterogeneity, we investigated their oc currence in relation to variables such as tumour volume, local invasio n, and biopsy findings. In a series of 61 completely sectioned whole-m ount radical prostatectomy specimens with clinical stage T2 prostate c ancer, we mapped histological grade heterogeneity and tumour multifoca lity. We also evaluated 55 prostate biopsy cases to assess the accurac y of pre-operative grading. Among all of the prostates, only 28 per ce nt had a single tumour and in 16 per cent one histological grade of ca ncer was evident. Extracapsular invasion was not restricted to the lar gest tumour in each case, but also occurred in tumours of relatively s mall volume and low histological grade. Variability of histological gr ade was directly proportional to tumour volume. Both grade heterogenei ty and tumour multifocality of the prostatectomy specimen showed no si gnificant relationship to the grade accuracy of biopsies. Biopsy gradi ng error proved greatest among small, well-differentiated tumours. Who le-mount sectioning of prostatectomy specimens in patients with clinic ally localized adenocarcinoma demonstrates that grade heterogeneity is most closely related to tumour volume; that the largest (index) tumou r lesion may not be representative of the pathological stage; and that grading error in prostate needle biopsies can be only partly explaine d by grade heterogeneity or tumour multifocality.