Cancer risk and genotype-phenotype correlation in Japanese patients with Cowden syndrome.

Background: Cowden syndrome (CS) is an autosomal-dominant hereditary disorder caused by a germline PTEN variant and characterized by multiple hamartomas and a high risk of cancers. However, no detailed data on CS in Asian patients nor genotype-phenotype correlation have been reported.

Methods: We performed the first Japanese nationwide questionnaire survey on CS and obtained questionnaire response data on 49 CS patients.

Results: Patients included 26 females (median age 48 years). The incidence of breast, thyroid, endometrium, and colorectal cancer was 32.7%, 12.2%, 19.2% (among females), and 6.1%, respectively. The incidence of any cancers was relatively high among all patients (46.9%, 23/49), and particularly female patients (73.1%, 19/26), compared with previous reports from Western countries. Gastrointestinal (GI) polyps were more frequently found throughout the GI tract compared with previous studies. PTEN variants were detected in 95.6% (22/23) of patients; 12 in the N-terminal region (11 in phosphatase domain) and 10 in the C-terminal (C2 domain) region. The incidence of cancer in the C2 domain group was significantly higher than in the N-terminal region (phosphatase) group. All female patients with C2 domain variant had breast cancer.

Conclusion: Our data suggest that Japanese patients with CS, particularly female patients and patients with C2 domain variant may have a high risk of cancers.