Myxoma is a benign tumor made up of mucous tissue. Is usually pale in color, round, lobulated, encapsulated, and feels semifluid. On section a thick, viscid fluid exudes.

Microscopically spindle and stellate cells with long processes that anastomose are seen. In the meshes between the cells and processes is the mucous material. This substance is precipitated by acetic acid.

They occur in sheaths of tendons and nerves and in nasal and pharyngeal polyps, and in combination with sarcoma. Mucoid growths forming from degeneration of fibromata are not true examples of myxomata.