Lymphadenopathy associated with a thyroid carcinoma in a dog

Area of Science:

• Veterinary Pathology
• Comparative Pathology
• Canine Neoplasia

Background:

• Thyroid carcinoma in dogs can metastasize to lymph nodes.
• Lymph node structure and function can be affected by neoplastic processes.
• Vascular lesions in lymph nodes require careful differentiation from metastatic disease.

Observation:

• Angiomatoid lesions were confined to subcapsular and medullary sinuses of a dog's lymph node.
• The lesions were associated with a concurrent thyroid carcinoma.
• Lymphoid tissue showed atrophy, but overall nodal architecture remained intact without invasion.

Findings:

• Immunohistochemistry revealed vascular spaces lined by endothelium with low mitotic activity.
• Spindloid cells stained positive for smooth muscle actin, vimentin, and desmin.
• These cellular markers suggest fibroblasts, myofibroblasts, smooth muscle cells, or pericytes contributed to the lesions.

Implications:

• The observed lesions resemble vascular transformation of lymph node sinuses (nodal angiomatosis) in humans.
• This condition is typically non-neoplastic and may result from lymphatic or venous blockage.
• Findings suggest a reactive vascular process rather than direct lymph node metastasis from the thyroid carcinoma.