Equine adenocarcinomas of the large intestine with osseous metaplasia.

The research article reports the rare case of two horses diagnosed with large intestinal adenocarcinoma that had developed osseous metaplasia. Both animals suffered from symptoms including weight loss and anaemia and consequently had to be euthanized.

Background

• The paper is a case report about two horses diagnosed with a rare condition – large intestinal adenocarcinoma with osseous metaplasia. Adenocarcinomas are malignant tumors that originate from epithelial cells, which are found in tissues that cover or line certain internal organs. Osseous metaplasia refers to a related condition where there’s a transformation of non-bone tissues into bone.

Patients and Diagnosis

• The patients were a 15-year-old standard bred gelding and a 9-year-old Haflinger mare.
• Both animals had displayed weight loss and anaemia. A presumptive diagnosis of abdominal neoplasia was made and the horses were humanely killed.

Necropsy Findings

• Upon post-mortem examination, the gelding and the mare were found to have ulcerated tumours growing into the lumen of the caecum and colon, respectively.
• The mare’s mass extended through the mesocolon and was evident in the left dorsal and ventral colon.
• Both tumors were well-circumscribed, meaning they could be clearly differentiated from the surrounding tissue, but had invaded the intestinal wall.
• No observable metastases were found, suggesting that the cancers hadn’t spread to other areas of the body.

Microscopic Examination

• The microscopic examination revealed that the tumors were made up of well-differentiated cords of a single layer of either columnar or cuboidal epithelial cells.
• Very few mitotic figures were seen, indicating a low index of cellular division, which is characteristic of well-differentiated tumors.
• Additionally, well-formed bony spicules and osteoid were present in the fibrovascular stroma, providing evidence of osseous metaplasia.