A relatively rare, usually benign neoplasm originating in the chemoreceptor tissue of the carotid body; glomus jugulare; glomus tympanicum; aortic bodies; and the female genital tract. 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. (From Stedman, 27th ed)