Possible Founder Effect of the CDKN2A c.146T>C Variant in the Mexican Population: Phenotypic Characterization

Background: Germline CDKN2A variants are associated with Familial Atypical Mole-Malignant Melanoma (FAMMM) syndrome. This syndrome involves an increased risk of melanoma, pancreatic cancer, and, in specific populations, duodenal cancer, breast cancer, and astrocytoma. The CDKN2A (c.146T>C) variant has been found in hereditary cancer patients within the Mexican population. Furthermore, the phenotype linked to this variant in Mexico differs from that observed in other groups. This study aims to evaluate the founder effect of the CDKN2A (c.146T>C) variant through epidemiological analysis and to describe the phenotype within our population. Patients and Methods: We examined 72 Mexican patients (14 probands from distinct families, 48 relatives, and 10 nonrelated probands) carrying the CDKN2A (c.146T>C) form three hereditary cancer centers between September 2023 and September 2025. Results: Of the 72 individuals analyzed, 52 (72.22%) tested positive. A cancer diagnosis was established in 27 (37.50%) of the individuals analyzed. Breast cancer was the most common neoplasia, accounting for 19 cases (70.37%), followed by melanoma with 4 cases (14.81%) and ovarian cancer with 2 cases (7.40%). Three patients (11.11%) had two distinct primary neoplasms. Conclusions: Based on our findings and the fact that this variant has been reported nearly exclusively in the Mexican population, we conclude that it has a founder effect in this population. Additionally, the phenotype associated with this variant can vary among populations, with breast cancer being the most common carcinoma rather than melanoma among Mexican carriers, highlighting the importance of updating screening guidelines.