PTEN and hereditary nonpolyposis colon cancer: In particular, Zhou and colleagues found that among 11 HNPCC CRC, 32 MSI sporadic cancer, and 39 microsatellite stable tumors, PTEN somatic mutations were found in 18, 13, and 0% of cases respectively, and PTEN loss of expression (evaluated by IHC) in 31, 41, and 17%, respectively.