Uterine adenocarcinoma—A rare cause of chronic weight loss in mares

Diagnosing the cause of slowly progressing weight loss in mares may be challenging, especially when only accompanied by non-specific and weak clinical signs and non-specific biochemical and haematological alterations. A 15-year-old mare presented with a history of weight loss, anorexia and fever. The most conspicuous clinical finding was enlarged ovaries. Abdominal fluid cytology revealed suspected tumour cells. Postmortem examination identified a primary uterine adenocarcinoma that had infiltrated adjacent structures and caused both peritoneal implantation metastases and distant metastases to multiple organs. The uterine adenocarcinoma was diagnosed when already in an advanced stage with widespread metastases and extensive infiltrative growth in multiple abdominal structures. Presence of uterine adenocarcinoma and other malignant uterine tumours should be ruled out as part of an initial clinical examination when mares, especially older mares, are presented with non-specific clinical signs and weight loss to ensure early recognition of such malignancies.