STK11 and Peutz-Jeghers syndrome: Also, patients may have already tested negative by another commercial lab for causative variants in one or more of the genes on the test, such as BRCA1 and BRCA2. Likewise, the number of patients in which a causative STK11 mutation was detected is low; in over 7,500 cases, all mutations in STK11 were identified in individuals who met clinical criteria for Peutz-Jegher polyposis.