Metastatic malignant cylindroma arising on a background of digenic inheritance of BRCA2 and CYLD pathogenic variants targeted with PARP inhibition.

Background: CYLD cutaneous syndrome (CCS) is caused by germline heterozygous pathogenic variants in CYLD and results in progressive formation of cylindromas, spiradenomas, or trichoepitheliomas. Malignant cylindroma is a rare skin adnexal tumour occurring in CCS that can metastasize with lethal outcomes and has limited genomic characterization. BRCA2 loss in CCS is not described and may modulate the cutaneous cancer risk of CCS.