The lesional fibrosis typically extends to the overlying stratified squamous epithelium but may be separated from it by a thin layer of normal fibrovascular connective tissue. While usually nonencapsulated, some lesions show a pseudo-encapsulation and may, therefore, be mistaken for neurofibroma or palisaded encapsulated neuroma. Scattered chronic inflammatory cells are seen in small numbers, usually beneath the epithelium or around blood vessels. Occasional fibromas demonstrate extreme elongation of rete processes and are called fibroepithelial polyps by some authorities, presumably because of their similarity to the dermal lesion of that name. These polyps are seen on the tongue in patients with Gorlin syndrome (nevoid basal cell carcinoma syndrome).
The surface epithelium is usually atrophic but may show signs of continued trauma, such as excess keratin, intracellular edema of the superficial layers or traumatic ulceration. The hyperkeratinized epithelium is not dysplastic or precancerous and is essentially a frictional keratosis. Rarely, melanin deposition is seen in the basal layer. This has no diagnostic significance but its presence has led some to refer to such a lesion as pigmented fibroma.