Leiomyosarcoma with widespread metastases in a capybara

Area of Science:

• Veterinary Pathology
• Comparative Oncology
• Rodent Medicine

Background:

• Leiomyosarcoma is a malignant smooth muscle tumor.
• Capybaras (Hydrochoerus hydrochaeris) are large South American rodents.
• Spontaneous tumors are infrequently reported in capybaras.

Purpose of the Study:

• To report a novel case of leiomyosarcoma in a capybara.
• To describe the clinical, postmortem, and histologic findings.
• To document the aggressive metastatic behavior of this tumor in a novel species.

Main Methods:

• Necropsy and gross examination of a deceased capybara.
• Histologic evaluation of tumor tissues from multiple organs.
• Immunohistochemical staining to confirm cell origin.

Main Results:

• A large uterine leiomyosarcoma with extensive local invasion was identified.
• Widespread metastases were found in the peritoneum, liver, lungs, and intestinal serosa.
• Immunohistochemistry confirmed the smooth muscle origin of the anaplastic spindle cells.

Conclusions:

• This case represents the first reported instance of leiomyosarcoma in a capybara.
• The widespread metastases indicate an unusually aggressive tumor behavior.
• An incidental dermal histiocytoma, also previously unreported in capybaras, was noted.