High-grade PIN displays four major patterns and several minor patterns. The major architectural patterns include tufting (shown here), flat, micropapillary, and cribriform. Minor patterns include signet ring, small cell, foamy gland, mucinous, and inverting type. The different architectural patterns appear to have no clinical significance and there are no known differences with regards to the risk of carcinoma on repeat biopsy. The glands displayed here show nuclear enlargement and hyperchromasia with prominent nucleoli.