CYLD and trichoblastoma: The definitive diagnosis of BSS is based on the combination of clinical and pathologic findings, including a clinical history of multiple skin neoplasms at a young age with a family history of similar neoplasms, biopsy findings of cylindroma, spiradenoma, or trichoepithelioma, the association with BCA or BCAC of the major or minor salivary glands, and the presence of a germline mutation in CYLD by genetic testing.