The c.5202T>G variant in BRCA1 is a missense variant predicted to cause substitution of Phenylalanine by Leucine at amino acid 1734 (p.(Phe1734Leu)). This variant is absent from gnomAD v2.1 (exomes only, non-cancer subset, read depth ≥25) and gnomAD v3.1 (non-cancer subset, read depth ≥25) (PM2_Supporting met). Reported by two calibrated studies to exhibit protein function similar to pathogenic control variants (PMID:30209399, 35196514) (PS3 met). This BRCA1 missense variant is within a key functional domain and the computational predictor BayesDel (noAF) gives a score of 0.27, indicating impact on BRCA1 function via protein change is unclear (score range 0.15-0.28). A SpliceAI score of 0 predicts no impact on splicing (score threshold <0.10) (no bioinformatic code is applied). A different nucleotide change leading to the same amino acid change (c.5200T>C p.Phe1734Leu, ClinVar Variation ID 125806) is classified as likely pathogenic by the ENIGMA BRCA1/2 VCEP. Splicing prediction revealed no effects on splicing due to either variant. These results suggest that the variant has an impact on protein consistent with pathogenicity (PS1_Moderate (Missense) met). In summary, this variant meets the criteria to be classified as a Likely pathogenic Variant for BRCA1-related cancer predisposition based on the ACMG/AMP criteria applied as specified by the ENIGMA BRCA1/2 VCEP (PM2_Supporting, PS3, PS1_Moderate (Missense)).