Choice of control tissue impacts designation of germline variants in a cohort of papillary thyroid carcinoma patients

•Tumor sequencing is often performed with paired non-tumor samples, allowing distinction of somatic from germline mutations.•Misdesignation of mutation origin has profound impact: screening, prophylactic intervention, clinical trial eligibility.•Even the healthy genome is subject to variation in the course of a lifetime, resulting in heterogeneity (somatic mosaicism).•As a result of somatic mosaicism, choice of non-tumor control tissue alters...