One sebaceous neoplasm underwent all tumour- and blood-based testing but no evidence of a germline MLH1 pathogenic variant, somatic MLH1 hypermethylation or MLH1 epimutation, or double somatic MLH1 mutations was identified, therefore, the cause of MLH1/PMS2-deficiency in this case was considered unexplained (Fig. 1). Here, PMS2 is linked to sebaceous gland neoplasm.