Postpartum breast cancer as a distinct oncologic entity: linking physiological tissue remodelling to tumor biology and clinical translation.

Postpartum breast cancer (PPBC), defined as breast cancer diagnosed within 10 years after childbirth, is increasingly recognized as a biologically distinct and clinically aggressive subtype affecting young women worldwide. The postpartum mammary gland undergoes extensive remodelling during involution, characterized by inflammation, extracellular matrix reorganization, and immune suppression, collectively creating a tumor-promoting microenvironment. Recent studies have revealed unique molecular features of PPBC, including alterations in immune composition, stromal activation, and selective pathway enrichment that distinguish it from breast cancers in nulliparous or age-matched parous women. While estrogen signalling remains an important regulatory axis during the postpartum period, its interplay with involution-associated processes and tumor behaviour requires further elucidation. In this review, we summarize current advances in understanding PPBC biology, highlight emerging biomarkers, and discuss evolving therapeutic considerations relevant to this high-risk population. We also provide an overview of ongoing clinical investigations, such as aspirin-based anti-inflammatory trials aimed at targeting postpartum-specific mechanisms that may contribute to tumor initiation or progression. Together, these insights emphasize the need for dedicated translational research and tailored clinical strategies to improve early detection, risk stratification, and outcomes for women diagnosed with PPBC.