Case Study

CT – Bilateral hyperplasia of the thyroid with large cyst in the left in a 15 year old MN Persian cat

This 15 year old MN Persian cat presented with a large mass on the neck. HCT 13%, decreased BUN, increased Crea.

DX

• Severe cystic enlargement of the left thyroid • Mild nodular enlagement of the right thyroid gland

Image Interpretation

CT of the neck-

The left thyroid gland presents severe symmetrical enlargement at 5 x 4 x 3 cm. The large fluid filled, non-enhancing center is surrounded by a thin rim of well-vascularized and markedly enhancing soft tissue. A significant centrifugal mass effect on the surrounding anatomy causes displacement of the common carotid artery, internal and external jugular vein, trachea and esophagus. Partial luminal obliteration & congestion of the carotid artery and jugular veins is noted. There is vascular collateral formation. However, there is no evidence of vascular invasion, vascular thrombosis or infiltrative growth of the enlarged thyroid gland. The right thyroid gland presents mild asymmetric enlargement with small multifocal nodular changes and non-uniform enhancement.

Outcome

Computed tomographic findings are suggestive for bilateral adenomatous hyperplasia of the thyroid gland with a large follicular cyst of the left thyroid gland. The changes do not meet malignancy criteria. A cystic thyroid carcinoma is considered very unlikely.
Adenomatous hyperplasia is accompanied by systemic hyperthyroidism in nearly all feline patients.
Screening for hyperthyroidism, systemic hypertension, and hypertensive cardiomyopathy & retinopathy is advised to plan further therapeutic management. Chronic renal failure may be compensated by the systemic hypertension.