Grading errors in prostatic needle biopsies: relation to the accuracy of tumor grade in predicting pelvic lymph node metastases.

To examine how accurately needle biopsies reflect the true histologic grade of prostatic cancers the histologic grade of needle biopsy specimens was compared to that of the radical prostatectomy specimen in 66 consecutive patients. Needle biopsies were given a lower grade than the prostatectomy specimen in 21 patients (33 per cent) and a higher grade in 5 patients (8 per cent). To examine how accurately the tumor grade of needle biopsy specimens predicts lymph node metastases in patients with clinical stage B prostatic cancer the needle biopsy grade was compared to lymph node metastases in 78 consecutive patients who underwent staging pelvic lymphadenectomy. Thirteen per cent of the patients with well differentiated cancer, 50 per cent with moderately differentiated cancer and 64 per cent with poorly differentiated cancer had pelvic lymph node metastases. In most cases grading errors did not influence the capacity of needle biopsies to predict nodal involvement. We conclude that although prostatic needle biopsies are associated with significant errors in grading they do provide valuable information about the predominant histologic pattern, which reflects the biologic potential of the tumor.