irritation fibroma irritation fibroma an irritation fibroma is a fibrous nodule of the oral cavity, often considered to be a reactive hyperplasia secondary to trauma or other local sources of irritation. irritation fibromaother namesoral fibroma, traumatic fibroma, focal fibrous hyperplasiahistopathology of irritation fibroma. low magnification (left) characteristically shows a nonencapsulated nodular mass. high magnification (right) shows fibrous connective tissue with collagen bundles, and some blood vessels and fibroblasts.specialtygastroenterologysymptomspalpable nodule