Gumma Definition A gumma is a soft, tumor-like growth of the tissues (granuloma) caused by syphilis. It appears during late stage, tertiary syphilis. It usually contains a mass of dead and swollen fiber-like tissue, and occurs most frequently in the liver but may also occur in the brain, testis, heart, skin, and bone. Also, similar-appearing granulomatous sores are sometimes found with tuberculosis |