Which of the following statements about carotid body tumors are true?

C. Carotid body tumors are extremely vascular.

D. Carotid body tumors most frequently present as a palpable, painless mass at the carotid bifurcation.

DISCUSSION: Cells of the carotid body function as receptors for changes in PO2, PCO2, and pH. Interestingly, carotid body tumors are more prevalent in persons living at high altitudes. Although carotid body tumor cells may have characteristics of malignancy, only about 5% of them metastasize. A carotid body tumor characteristically appears as a hypervascular oval mass situated at the carotid bifurcation and widening the angle between the origins of the internal and external carotid arteries. Although large or malignant carotid body tumors may cause dysfunction of the vagus and hypoglossal nerves and cause dysphagia from their mass effect on the hypopharynx, most tumors are recognized when they still have no associated symptoms and are only a painless mass over the area of the carotid bifurcation