Fibrous growths of the oral soft tissues are fairly common and include a diverse group of reactive and neoplastic conditions. Some of these conditions are discussed elsewhere in Medscape Drugs & Diseases. For example, the term epulis fissuratum refers to epithelial and fibrous hyperplasia specifically related to, and the result of, trauma from the border of a removable denture. It may be viewed as the mucosal counterpart of acanthoma fissuratum.
See the image below depicting fibrous tumorlike growth of the oral soft tissues.
The fibroma, also referred to as irritation fibroma, is by far the most common of the oral fibrous tumorlike growths. While the terminology implies a benign neoplasm, most if not all fibromas represent reactive focal fibrous hyperplasia due to trauma or local irritation. Although the term focal fibrous hyperplasia more accurately describes the clinical appearance and pathogenesis of this entity, it is not commonly used.
A fibroma may occur at any oral site, but it is seen most often on the buccal mucosa along the plane of occlusion of the maxillary and mandibular teeth as depicted below.  It is a round-to-ovoid, asymptomatic, smooth-surfaced, and firm sessile or pedunculated mass. The diameter may vary from 1 mm to 2 cm. The surface is usually similar in color to the surrounding mucosa but may be hyperkeratotic or ulcerated, owing to repeated trauma.
Fibromas are most often observed in adults, but they may occur in individuals of any age and either sex.
The clinical differential diagnosis of a fibroma depends on its clinical presentation and location and includes giant cell fibroma, neurofibroma, peripheral giant cell granuloma, schwannoma, granular cell tumor, mucocele, and benign and malignant salivary gland tumors (eg, see Salivary Gland Neoplasms).
Histologically, a fibroma is an unencapsulated, solid, nodular mass of dense and sometimes hyalinized fibrous connective tissue that is often arranged in haphazard fascicles. A mild chronic inflammatory infiltrate may be present. The surface epithelium may be hyperkeratotic, hyperplastic or atrophic, and ulcerated. Conservative excisional biopsy is curative, and its findings are diagnostic. Recurrence is possible, however, if the offending irritant persists. [2, 3]
The elastofibroma is a rare dermatologic pseudotumor most often seen in the subscapular region. Patients tend to be older than 50 years, and some studies show a female predominance. Although involvement of the oral cavity is rare, few cases of oral elastofibromas have been documented in the literature, presenting as asymptomatic submucosal and nodular masses involving the floor of the mouth and hard palate. Surgical excision is the treatment of choice. Histologically, the elastofibroma consists of collagen fibers and coarse elastic fibers that can be demonstrated with elastin stain. [4, 5, 6]
The sclerotic fibroma was first described as a component of Cowden syndrome. It is an uncommon benign fibrous neoplasm that occurs most commonly in the skin and may be solitary or multifocal. Both sporadic sclerotic fibromas and those associated with the syndrome have also been described in the oral cavity, mainly in the buccal and labial mucosa. The tumor is a well-delineated but unencapsulated mass of densely collagenized, hypocellular fibrous tissue with a storiform pattern and prominent clefts between collagen bundles. The tumor cells are CD34 and vimentin positive. [7, 8]
Giant Cell Fibroma
Giant cell fibroma is the oral counterpart of fibrous papule of the nose. It appears as an asymptomatic sessile or pedunculated nodule that is smaller than 1 cm in diameter. Often, it has a bosselated or somewhat papillary surface. Most cases are diagnosed in persons aged 10-30 years. No sex predilection has been reported. The most common sites are the mandibular gingiva, followed by the maxillary gingiva, the tongue, and the palate.
Microscopically, a giant cell fibroma is an unencapsulated mass of fibrous connective tissue that contains numerous characteristic large, plump, spindle-shaped and stellate fibroblasts, some of which are multinucleated. These cells are easily observed in the peripheral areas of the lesion, while the more central areas contain typical fusiform fibroblasts. The surface epithelium is often corrugated and atrophic. In contrast to an irritation fibroma, a giant cell fibroma has thin, elongated rete ridges.
Peripheral Cemento-ossifying Fibroma
A peripheral cemento-ossifying fibroma is also known as a peripheral ossifying fibroma, a calcifying fibrous epulis, or a peripheral fibroma with calcification. It is a reactive gingival lesion that is believed to arise from cells of the periodontal ligament or periosteum. Most often, it is located in the gingival papilla between adjacent teeth. A peripheral cemento-ossifying fibroma manifests as a sessile or pedunculated mass, which is often ulcerated and generally has a diameter of less than 2 cm as shown below. Peripheral cemento-ossifying fibromas may occur in persons of any age but are most often seen in persons aged 10-20 years. Females are affected more often than males by a ratio of approximately 3:2.
The maxillary gingiva is involved more often than the mandibular gingiva; usually, the anterior region is affected. Mobility and/or migration of adjacent teeth is occasionally observed as depicted in the image below. 
Microscopically, fibrous proliferation is accompanied by increased cellularity with plump, immature fibroblasts and variable amounts of calcified material. This material may be osteoid, cementoid, or dystrophic. In some cases, this characteristic pattern is only part of the pattern of a larger lesion that may resemble an irritation fibroma or pyogenic granuloma. Surface ulceration is common. 
The clinical differential diagnosis of a peripheral cemento-ossifying fibroma includes inflammatory gingival hyperplasia, peripheral giant cell granuloma, pyogenic granuloma, fibroma, and peripheral odontogenic fibroma.
Treatment consists of excision down to the periosteum and the elimination of any local irritants. Care must be taken to maintain or reestablish acceptable gingival architecture and periodontal integrity. A recurrence rate of 16% is reported. Even in cases complicated by recurrence, reexcision is generally successful, with the retention of the associated teeth. [3, 13, 14, 15, 16, 17, 18]
Peripheral Odontogenic Fibroma
A peripheral odontogenic fibroma is a rather uncommon neoplasm that is believed to arise from odontogenic epithelial rests in the periodontal ligament or the attached gingiva itself. The entity, formerly confused with peripheral cemento-ossifying fibroma, is considered to be the extraosseous counterpart of the central odontogenic fibroma of the World Health Organization type.  A peripheral odontogenic fibroma manifests as a firm, slowly growing, sessile, and nodular growth of the gingiva, most often on the mandibular buccal or labial aspect, which may cause displacement of teeth as depicted below. It occurs in persons of a wide age range, with a slight predilection for females. 
The clinical differential diagnosis of a peripheral odontogenic fibroma includes inflammatory gingival hyperplasia, peripheral cemento-ossifying fibroma, and peripheral giant cell granuloma.
Microscopically, the tumor consists of an unencapsulated mass of interwoven cellular fibrous connective tissue that contains scattered nests or strands of odontogenic epithelium. Myxoid foci, osteoid, cementoid, or dystrophic calcifications are sometimes seen. The surface generally is not ulcerated.
Treatment consists of conservative excision performed with care to maintain or reestablish the gingival architecture and periodontal integrity. The recurrence rate is generally considered to be low. However, a recurrence rate of up to 50% has been documented in the literature. [20, 21, 22, 23]
The fibromatoses represent a group of infiltrating fibrous proliferations with a biologic behavior and microscopic appearance intermediate between those of benign fibrous lesions and fibrosarcomas. In the head and neck region, they are sometimes referred to as juvenile or aggressive juvenile fibromatoses, as well as extraabdominal desmoids. Patients of any age may be affected, but three quarters of all cases are diagnosed when the patient is younger than 10 years. No significant sex predilection is apparent.
The most frequent site of occurrence is the soft tissues adjacent to the mandible. However, the lesion can occur anywhere and involvement of the temporomandibular joint has been reported. Intraoral presentations are rare, but they most often involve the tongue or buccal mucosa. Lesions appear as firm, painless, poorly demarcated masses with a variable growth rate. They are locally aggressive and often cause resorption of the underlying bone when present. A desmoplastic fibroma occurring within the medullary cavity of bone is considered to be the intraosseous counterpart of the soft tissue fibromatosis. [24, 25, 26]
The differential diagnosis of a soft tissue fibromatosis is myofibroma and rhabdomyosarcoma.
Microscopically, fibromatosis is characterized by a poorly delineated, infiltrating cellular proliferation of mature spindle cells arranged in streaming and interlacing fascicles. Collagen production is usually prominent. Infiltration of the adjacent structures is common at the periphery, but cellular atypia is not present.
Treatment consists of wide excision, owing to its locally aggressive nature. The reported recurrence rate is 30%, and the risk of recurrence is greatest in the first year after treatment. Long-term follow up is recommended. It is not known to metastasize. [27, 28, 29, 30, 31, 32, 33]
Gingival fibromatosis deserves separate consideration. It may be hereditary, idiopathic, or drug induced. The hereditary and idiopathic forms manifest as isolated or diffuse firm, noninflammatory enlargements of the keratinized gingiva. Although the process is typically nonpainful, the enlarged gingiva may eventually cover large portions of the clinical crowns of teeth and erode the underlying bone. Recurrence is common following surgical excision. The hereditary form may also manifest as a component of a larger complex syndrome (eg, gingival fibromatosis with hypertrichosis syndrome, Zimmermann-Laband syndrome, Cross syndrome). Both the idiopathic and hereditary forms are rare, limited to the gingiva, and most often affect children. Drug-induced gingival overgrowth has been associated with systemic use of phenytoin, cyclosporin, and calcium channel blockers. [34, 35, 36, 37, 38]
Myofibroma and Myofibromatosis
Myofibroblasts are spindle-shaped cells with features of both fibroblasts and smooth muscle cells. Myofibroblasts have been identified in lesions other than myofibromas, but when they are the predominant cell type in a tumor, the terms myofibroma (if solitary) or myofibromatosis (if multicentric) are applied. The tumors are benign, and, although myofibromatosis is similar to fibromatosis in many ways, its behavior tends to be less aggressive. Tumors of myofibroblasts may occur in either sex. Solitary tumors develop in patients at a mean age of 22 years, while multicentric myofibromatosis primarily affects neonates and infants.
Solitary myofibromas have a head and neck predilection, with the mandible being the most common site of occurrence. The most common oral soft tissue sites are the tongue, lips, and buccal mucosa. Tumors also have been described in the dermis, soft tissues, viscera, and bone. Intraosseous jaw lesions most often manifest as well-defined unilocular or multilocular radiolucencies. Oral soft tissue lesions typically manifest as firm, slow growing, submucosal nodules or exophytic masses with a diameter of 0.3-5 cm. Although patients are frequently asymptomatic, the lesions may be tender or even painful.
The clinical differential diagnosis for oral myofibroma includes irritation fibroma, fibromatosis, peripheral giant cell fibroma, neurofibroma, leiomyoma, and benign and malignant neoplasms of the minor salivary glands (eg, see Salivary Gland Neoplasms).