Most urologists would agree that an initial evaluation should always biopsy.
High grade PIN is associated with a fairly high risk of developing adenocarcinoma within 5 years. The real controversy here however is the use of the saturation biopsy to detect low levels of malignancy within the prostate. Saturation biopsies have been reported to increase the detection rate of prostate cancer. Given that prostate cancer is usually a slow growing cancer, many urologists would favor close follow-up in 3-6 months. Part of the decision process of whether to proceed with saturation biopsies would depend on how extensive the PIN was in the original biopsies.