Epigenetic dysregulation underpins tumorigenesis in a cutaneous tumor syndrome

Patients with CYLD cutaneous syndrome (CCS; syn. Brooke-Spiegler syndrome) carry germline mutations in the tumor suppressor CYLD and develop multiple skin tumors with diverse histophenotypes 1,2 . We comprehensively profiled the genomic landscape of 42 benign and malignant tumors across 13 individuals from four multigenerational families. Novel driver mutations were found in epigenetic modifiers DNMT3A and BCOR in 29% of benign tumors. Multi-level and microdissected sampling strikingly reveal that many clones with different DNMT3A mutations exist in these benign tumors, suggesting that intra-tumor heterogeneity is common. Integrated genomic and methylation profiling suggest that mutated DNMT3A drives tumorigenesis mechanistically through Wnt/ß-catenin pathway signaling. Phylogenetic and mutational signature analyses confirm the phenomenon of benign pulmonary metastases from primary skin lesions. In malignant tumors, additional epigenetic modifiers MBD4 , CREBBP, KDM6A and EP300 were mutated. We thus present epigenetic dysregulation as a driver in CCS tumorigenesis and propose this may account for the diverse histophenotypic patterns despite the paucity of mutations seen. These findings add novel dimensions to existing paradigms of cutaneous tumorigenesis and metastasis.