Background: In Mexico, breast cancer (BCa) is in first place regarding cancer mortality and has been established as a priority health issue. The incidence of metastasis from BCa is very high and presents as the principal mortality factor among women younger than 40 years of age. OBJECTIVE. To determine any associations between clinicopathological characteristics and metastasis in Mexican women under 40 years of age. Methods: During the 2010–2015 period, a total of 180 female BCa cases seen at the Navy General High Specialty Hospital, SEMAR, in Mexico City; we collected information on 20 patients with BCa younger than 40 years of age. Statistical analyses were conducted using the Kolmogorov–Smirnov, Students t, Fisher, Chi square, and Mantel–Haenszel tests. Results: The prevalence of women with BCa younger than the age of 40 years during the 2010–2015 period was 13.3%. We found a high frequency of obesity in of these cases (>75%); 100% of obese patients with a history of smoking presented with metastasis (p <0.05). In addition, the hormone phenotype was important; HER2-positive cases were 12 times more likely tto exhibit metastasis (p <0.05), while expression of estrogen and progesterone receptors appeared to be protective. Diabetes mellitus in combination with smoking was also a risk factor for development of metastasis (p <0.05). Conclusion: In this study, we obtained essential data regarding risk of metastasis in young breast cancer cases which could be useful for predicting disease evolution and treatment response.