Microenvironment of the involuting mammary gland mediates mammary cancer progression.

Breast cancer diagnosed after a completed pregnancy has higher metastatic potential and therefore a much poorer prognosis. We hypothesize that following pregnancy the process of mammary gland involution, which returns the gland to its pre-pregnant state, co-opts some of the programs of wound healing. The pro-inflammatory milieu that results, while physiologically normal, promotes tumor progression. In this review, the similarities between mammary gland involution after cessation of milk-production and pathological tissue remodeling are discussed in light of emerging data demonstrating a role for pathological tissue remodeling in cancer.