Confirmed hyperthyroidism secondary to minimally asymmetric bilateral thyroid masses typical in appearance for benign thyroid adenomas. Additional subtle increase in radionuclide distribution cranial to the left thyroid lobe with associated mass effect displacing both thyroid lobes caudally and to the right.

Two, large mixed echogenicity masses are noted cranial to both moderately enlarged thyroid lobes. The left thyroid lobe contains a single internal cystic region.

Multiple, large, ventral cervical masses with associated regional lymphadenopathy that proved to be an undifferentiated sarcoma on histopathologic evaluation.

Widely metastatic undifferentiated sarcoma. Hyperthyroidism secondary to benign bilateral thyroid adenoma/cystadenoma.

Palliative therapy was pursued and the patient was ultimately euthanized.

Broome M.R., Thyroid Scintigraphy in Hyperthyroidism. Clin Tech Small Anim Pract, 2006. 21(1): p. 10-6.