Carotid body tumor: an incidental finding in older ranch mink.

Carotid body tumors were found incidentally at necropsy in 15 ranch mink (Mustela vision), mostly royal pastels, kept for studies on slow viral diseases. The mink, five males and ten females, were 77 to 135 months old (mean age 107 months). Loosely or firmly attached at the bifurcation of the common carotid artery, and 11 larger tumors were smooth-surfaced, discrete, pale brown, globoid masses that varied from 2.5 to 16 mm in diameter. Four tumors of microscopic size occurred in otherwise normal-looking carotid bodies. All were composed of densely packed polygonal cells disposed in sheets and cords or arranged in clusters by a reticulin meshwork rich in blood vessels. Always unilateral, the tumors had not invaded locally or metastasized. As seen in the smallest tumors, the neoplastic cells usually arose centrally in the carotid body and formed an expansive growth that replaced much of the normal parenchyma without necessarily enlarging the organ beyond normal limits. The cause of the tumors was not apparent. All tumor-bearing mink had lived at an elevation of 1,100 meters, and none had suffered from any obvious chronic cardiopulmonary disease.