A RETROSPECTIVE REVIEW OF THE HISTOPATHOLOGICAL FEATURES SEEN IN A SERIES OF 4241 ENDOMETRIAL BIOPSY SAMPLES COLLECTED FROM UK THOROUGHBREDMARES OVER A 25 YEAR PERIOD

A retrospective review of the histopathological features and the group s in which they are most frequently seen in combination, seen in 4214 endometrial biopsy samples collected from UK Thoroughbred mares over a 25 year period revealed data which supports widely held views on thei r pathogenesis and significance. Endometrial hypoplasia is most common ly seen in young mares with delayed endometrial maturity. Mononuclear cell infiltrations develop in the endometrial stroma as a reflection o f local immune responses to challenge by seminal proteins, micro-organ isms, environmental debris and the products of pregnancy, during a bro od mare's life. Endometrial hyperplasia most commonly persists during delayed post parium or post-pregnancy failure of uterine involution, m ore commonly in younger mares. Glandular degenerative changes and stro mal fibrosis develop as an inevitable consequence of ageing, eventuall y leading to endometrial atrophy, a reflection of gynaecological senil ity. These degenerative changes result in endometrial incompetence, pr ogressively reducing mares' foaling potentials and increasing their po tential for barren years, early pregnancy failures and abortions.