Adrenocortical carcinoma in a 12-year-old mare.

The research article discusses the case study of a 12-year-old mare diagnosed with adrenocortical carcinoma, a type of adrenal gland tumor. Despite normal cortisol concentration levels, the tumor affected the horse’s health, causing colic and weight loss.

Case Description

• The research focuses on a 12-year-old Dutch warmblood mare who had been showing signs of colic intermittently over a few years and noticed to have lost weight over the past two months. These symptoms prompted a deeper investigation into the mare’s health.

Clinical Findings and Diagnosis

• A large firm mass was found in the horse’s left sublumbar region during the palpation per rectum examination. This mass was categorised postmortem as adrenocortical carcinoma, which is a rare and aggressive form of adrenal cancer. The horse, however, had a basal plasma cortisol concentration of 94 nmol/litre at 10:00, which is considered within the normal range. This finding was surprising as tumors like adrenocortical carcinoma usually disrupt normal adrenal gland function, often leading to abnormal cortisol levels.

Broader Context

• Despite the commonality of pituitary-adrenocortical axis tumors in horses, those specifically occurring in the adrenal gland like this case, are rare. To illustrate, only one out of the 21 horses examined by the authors for a neoplasm of the pituitary-adrenocortical axis had the tumor located in the adrenal gland.
• This study suggests that horses can have functional adrenocortical tumors without showing abnormal cortisol levels, challenging conventional understanding of such illnesses.