Anterior distribution of Stage T1c nonpalpable tumors in radical prostatectomy specimens.

OBJECTIVES: To determine the anatomic patterns of tumor distribution in radical prostatectomy specimens from nonpalpable prostate cancer. METHODS: Tumor maps directly traced from histologic slides of 62 radical prostatectomy specimens were superimposed by a computer-assisted imaging technique to create an idealized prostate gland at three levels: apex, mid-prostate, and base. To investigate specific patterns of tumor distribution, the sites of tumor in each quadrant were compared according to risk group stratification. The tumor extent was compared with the patterns of positivity in routine sextant biopsies. RESULTS: Among all patients, the tumor frequency was 85.5% in the mid-gland, 82.3% in the apex, and 48.4% in the base. Analysis by quadrant showed that tumors were significantly denser in the apex to mid-prostate. The primary extent of these tumors appeared to lie predominantly in the anterior half of the gland. Biopsy yields at the apex and mid-prostate appeared low compared with the frequency of cancers at these levels. No patterns specific to the different risk groups were found, but no tumors within the anterior base were found in the low-risk group. CONCLUSIONS: The primary extent of nonpalpable tumors appeared to lie predominantly in the anterior half of the gland at the apex to mid-prostate levels. Additional biopsy cores taken from more anterior regions of the gland may enhance the detection of nonpalpable cancers further.