Resumen: This study evaluates whether serum phospholipids fatty acids (PL-FAs) and markers of their endogenous metabolism are associated with breast cancer (BC) subtypes. EpiGEICAM is a Spanish multicenter matched case-control study. A lifestyle and food frequency questionnaire was completed by 1017 BC cases and healthy women pairs. Serum PL-FA percentages were measured by gas chromatography-mass spectrometry. Conditional and multinomial logistic regression models were used to quantify the association of PL-FA tertiles with BC risk, overall and by pathological subtype (luminal, HER2+ and triple negative). Stratified analyses by body mass index and menopausal status were also performed. Serum PL-FAs were measured in 795 (78%) pairs. Women with high serum levels of stearic acid (odds ratio (OR)T3vsT1 = 0.44; 95% confidence interval (CI) = 0.30-0.66), linoleic acid (ORT3vsT1 = 0.66; 95% CI = 0.49-0.90) and arachidonic to dihomo-¿- linolenic acid ratio (OR T3vsT1 = 0.64; 95% CI = 0.48-0.84) presented lower BC risk. Participants with high concentrations of palmitoleic acid (ORT3vsT1 = 1.65; 95% CI = 1.20-2.26), trans-ruminant palmitelaidic acid (ORT3vsT1 = 1.51; 95% CI = 1.12-2.02), trans-industrial elaidic acid (ORT3vsT1 = 1.52; 95% CI = 1.14-2.03), and high oleic to stearic acid ratio (ORT3vsT1 = 2.04; 95% CI = 1.45-2.87) showed higher risk. These associations were similar in all BC pathological subtypes. Our results emphasize the importance of analyzing fatty acids individually, as well as the desaturase activity indices. Idioma: Inglés DOI: 10.3390/nu12103132 Año: 2020 Publicado en: Nutrients 12, 10 (2020), 3132 [18 pp] ISSN: 2072-6643 Factor impacto JCR: 5.717 (2020) Categ. JCR: NUTRITION & DIETETICS rank: 17 / 88 = 0.193 (2020) - Q1 - T1 Factor impacto SCIMAGO: 1.417 - Nutrition and Dietetics (Q1) - Food Science (Q1)