PTEN and Cowden disease: However, a paper published in 1998 by the group of Eng and co-workers reported that PTEN loss-of-function mutations might not contribute to tumorigenesis to the same extent as the genetic loss of PTEN. This study was conducted on patients affected by Cowden disease, a PTEN hamartoma tumor syndrome, and revealed that patients with missense PTEN mutations in the phosphatase domain developed higher numbers of lesions compared to patients with truncating mutations (1).