Introduction: Because of its high incidence, breast cancer is the subject of numerous studies today. Despite being an uncommon disease in young women, when it affects this population, it tends to be more aggressive and has high mortality rates. Objective: The objective of this study was to evaluate the prognostic factors present in the immunohistochemical profile of young women with breast cancer, comparing the age groups of very young women (<35 years old — Group I) and young women (between 35 and 40 years old — Group II), to see if the data obtained match what is reported in the literature. Methods: A cross-sectional study was carried out, analyzing the immunohistochemical tests of 90 female patients with invasive breast carcinoma. The groups were classified on the basis of molecular subtype: luminal A, luminal B, hybrid luminal, human epidermal growth factor receptor 2 positive and triple-negative. Results: The histological type with the highest incidence was invasive breast carcinoma of no special type. The most frequent molecular subtypes were luminal B and triple-negative. With regard to estrogen and progesterone receptors, there was a slight predominance of positive receptors. Ki-67 levels showed that in the triple-negative and human epidermal growth factor receptor 2 positive subtypes, there was a predominance of high cell proliferation index. Conclusion: In the population of young women in this cohort of patients, there was agreement with literature data regarding the predominance of the invasive carcinoma of no special type histological type and the luminal B and triple-negative molecular subtypes, and the presence of high cell proliferation rates, attesting to the higher prevalence of more aggressive tumors in the younger population. There was also no statistically significant difference in all aspects analyzed when comparing Groups I and II. However, a higher frequency of negative hormone receptors or overexpressed human epidermal growth factor receptor 2 molecular subtypes was not detected, characteristics that are common to young women with breast cancer, which has been pointed out in several studies worldwide.