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A relatively rare, usually benign neoplasm originating in the chemoreceptor tissue of the carotid body, glomus jugulare, and aortic bodies. It consists histologically of rounded or ovoid hyperchromatic cells that tend to be grouped in an alveolus-like pattern within a scant to moderate amount of fibrous stroma and a few large thin-walled vascular channels. They are uncommon before the age of 20, with a female predominance in some series. (Stedman, 25th ed; from DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p570-1)