This is a noninflammatory enlargement or a hyperplasia of the thyroid gland.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
In some cases the hyperplasia affects chiefly the blood vessels of the thyreoid-vascular goitre.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition."
Alexander Miles Alexis Thomson
The rest of the gland may be normal, or may show some degree of hyperplasia.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition."
Alexander Miles Alexis Thomson