The NM_000546.6: c.328C>G variant in TP53 is a missense variant predicted to cause substitution of arginine by glycine at amino acid 110 (p.Arg110Gly). This variant is absent from gnomAD v4.1.0 (PM2_Supporting). Although this variant has been observed in germline cases, to our knowledge, this variant has not been reported in individuals meeting classical LFS or Chompret criteria (PS4 not met; Internal lab contributors). In vitro assays performed in yeast and/or human cell lines showed non-functional transactivation and loss of growth suppression activity indicating that this variant impacts protein function (PS3; PMIDs: 12826609, 30224644, 29979965). 2 different missense variants (p.Arg110Leu, p.Arg110Pro) (ClinVar Variation IDs: 406597, 233627), in the same codon have been classified as pathogenic for Li-Fraumeni syndrome by the ClinGen TP53 VCEP’s specifications. (PM5_Strong). Computational predictor scores (BayesDel = 0.056; Align GVGD Class C15) are below the recommended thresholds (BayesDel < 0.16 and > -0.008 and an Align GVGD Class ≤ 55), evidence that does not predict a damaging effect on TP53 via protein change. SpliceAI predicts that the variant has no impact on splicing (BP4). In summary, this variant meets the criteria to be classified as Likely Pathogenic for Li Fraumeni syndrome based on the ACMG/AMP criteria applied, as specified by the ClinGen TP53 VCEP: PM2_Supporting, PS3, PM5_Strong, BP4. (Bayesian Points: 8; VCEP specifications version 2.3)