Breast Cancer in Young Women and Contemporary Screening Policies: A Reflection from Global and Latin American Epidemiology

Breast cancer currently represents one of the leading global public health challenges due to its high incidence, mortality, and substantial societal impact. Although the disease has historically been more prevalent among postmenopausal women, growing concern has emerged over recent decades regarding the behavior of breast cancer in younger women and the need to adapt population-based early detection strategies accordingly. The recent decision by the Spanish healthcare system to expand its population-based breast cancer screening program from women aged 50–69 years to those aged 45–74 years reflects this evolving perspective, driven by contemporary epidemiological evidence and by recognition that a clinically meaningful proportion of tumors occur before the age of 50.

Recent data derived from the GLOBOCAN 2022 analysis for Latin America and the Caribbean reveal a particularly challenging scenario. More than 1.5 million new cancer cases and approximately 749,000 cancer-related deaths were recorded in the region during 2022. Breast cancer was the most common malignancy among women and the leading cause of cancer-related mortality in the female population, highlighting a growing healthcare burden. Furthermore, approximately 17% of new cancer diagnoses occurred in individuals with early-onset disease (15–50 years), underscoring the need to reconsider prevention and detection strategies that are more sensitive to age groups traditionally considered at lower risk.

However, properly interpreting the phenomenon of “young-onset breast cancer” requires rigorous epidemiological analysis. For years, it was hypothesized that less developed countries experienced a biologically higher incidence of premenopausal breast cancer. Nevertheless, Ghiasvand and colleagues demonstrated that this perception may be partially explained by demographic factors. Although less developed countries show a greater relative proportion of breast cancer cases diagnosed before the age of 50, age-adjusted incidence rates reveal a different reality: the actual incidence of premenopausal breast cancer remains higher in developed countries. The apparent “younger profile” of breast cancer observed in lower-resource settings is largely explained by demographic structure, including a smaller proportion of older women and differences in the prevalence of risk factors associated with postmenopausal breast cancer.

Even so, breast cancer in young women remains a clinically important entity. Patients younger than 40 years frequently present with biologically more aggressive tumors, higher histologic grade, increased proliferative indices, greater HER2 overexpression, and a higher prevalence of triple-negative disease. In addition, young women often exhibit higher rates of nodal involvement, multifocal disease, and predisposing genetic mutations, factors associated with less favorable oncologic outcomes. Diagnostic challenges related to dense breast tissue further complicate evaluation in younger women and may contribute to clinically relevant diagnostic delays.

These clinical challenges help explain the rationale behind the progressive expansion of breast cancer screening policies in Spain. Although screening programs must carefully balance benefits and harms—including overdiagnosis, false-positive findings, and unnecessary procedures—the epidemiological transition observed worldwide requires continuous reassessment of optimal screening ages. Future progress will likely involve not only expanding population coverage but also advancing toward more personalized screening strategies integrating age, genetic susceptibility, breast density, family history, and tumor biological characteristics.

Contemporary epidemiology demonstrates that breast cancer in young women is a clinically relevant phenomenon whose interpretation requires careful distinction between population proportions and age-adjusted incidence rates. Simultaneously, the growing cancer burden across Latin America and other regions underscores the need to strengthen prevention strategies, early detection initiatives, and equitable access to specialized cancer care. Expanding screening programs represents an important step forward; however, the future of breast cancer control will likely depend on increasingly individualized, risk-based preventive medicine approaches.