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A blue-red, extremely painful paraganglioma involving a glomeriform arteriovenous anastomosis (glomus body), which may be found anywhere in the skin, most often in the distal portion of the fingers and toes, especially beneath the nail. They may also occur in the stomach and nasal cavity. It is composed of specialized pericytes (sometimes termed glomus cells), usually in single encapsulated nodular masses which may be several millimeters in diameter. When located in the usual subungual site, the abundant innervation makes the tumor exquisitely painful; when located elsewhere, the glomus tumor is painless. (From Dorland, 27th ed; Stedman, 25th ed; Segen, Dictionary of Modern Medicine, 1992)