Myofibroma of the mandible: a case report.
Subject: Tumors
Authors: Lyons, Collins T.
Welch, Preston Q.
Flint, David C.
Snyder, Harold B.
Pub Date: 10/01/2012
Publication: Name: U.S. Army Medical Department Journal Publisher: U.S. Army Medical Department Center & School Audience: Professional Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2012 U.S. Army Medical Department Center & School ISSN: 1524-0436
Issue: Date: Oct-Dec, 2012
Topic: Canadian Subject Form: Tumours
Accession Number: 309980594
Full Text: CASE HISTORY

The patient was a white male aged 28 years whose medical history was noncontributory. He was afebrile with no lymphadenopathy or trismus. He presented to the dental clinic with a chief complaint of pain and swelling in the lower right jaw that was unresolved after scaling and root planing. The patient stated that the swelling started approximately 1 to 2 months prior to his reporting to the dental clinic. The oral examination revealed good oral hygiene, minimal gingival inflammation, and no carious lesions. Teeth No. 30 and 31 had been restored with gold onlays that were in good condition. Buccal swelling was evident in the 30-31 area that was firm, fibrotic, and painful to palpation (Figure 1). Teeth No. 30 and 31 responded within normal limits to vitality testing and were negative to percussion. A complete periodontal examination was performed and the patient was periodontally healthy. A radiographic examination revealed a unilocular radiolucency that extended from the furcation entrance close to the apices of the mesial and distal root of tooth No. 30. The radiolucency did not involve tooth No. 31, and the periodontal ligament was intact around both molars (Figure 2). The differential diagnosis included: periodontal abscess, fibrotic lesions, and odontogenic tumor.

SURGICAL PROCEDURE

After administering an inferior alveolar nerve block in the right mandible, mucoperiosteal flaps were elevated from teeth No. 28-31. Upon flap reflection, extensive resorption of the buccal plate in tooth No. 30 area was revealed. An incisional biopsy was performed to diagnose the lesion and determine a course of treatment. The flaps were closed with 4-0 vicryl and the patient scheduled for suture removal and a review of the oral pathology report. A week later the microscopic examination of the specimen confirmed a diagnosis of myofibroma. The results were reviewed with the patient and subsequent removal of the lesion scheduled. Several weeks later the patient returned for removal of the myofibroma. An inferior alveolar nerve block was performed in the lower right mandible. Mucoperiosteal flaps were reflected exposing the fibrotic lesion and the severe erosion of the buccal plate (Figures 3 and 4). The interproximal bone levels were within normal limits and the buccal furcation was intact despite the missing buccal plate. The entity was surgically excised (excisional biopsy) and the specimen placed in 10% formalin. The area was thoroughly debrided and osteoplasty performed. The surgical site was closed with 4-0 vicryl and postoperative instructions reviewed. Acetaminophen with codeine and chlorhexidine mouth rinse was prescribed. An ice pack was given to the patient to minimize swelling. The patient returned one week later for suture removal.

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GROSS AND MICROSCOPIC FINDINGS

The specimen was received in a container of 10% formalin and consisted of multiple soft tissue masses measuring from 0.3 cm to 1.5 cm at its greatest dimension. The largest specimen was serially sectioned (Figure 5). Microscopically, the tumors are well-defined or infiltrative, (1) arranged in whorls or short interlacing fascicles of spindled shaped myofibroblastic cells (Figure 6). (2) These cells appear intermediate between smooth muscle cells and fibroblasts (1) and have pale pink cytoplasm. The nuclei are elongated and blunt-ended with a vesicular chromatin pattern and one or 2 small basophilic nucleoli. Interspersed between the whorls of eosinophilic myoid cells are more cellular areas of primitive rounded, polygonal, or somewhat spindled shaped cells. These cells have limited cytoplasm and larger hyperchromatic nuclei. (2) These areas are highly vascular with branching hemangiopericytoma-like endothelial lined vascular channels and are usually concentrated in the center of the tumor. (3-6) At low power the pattern between the 2 cell types is described as having a biphasic or zoned appearance. (3,4,6,7) Pleomorphism or atypia are not expected features, however, focal calcification, stromal hyalinization, and necrosis are sometimes present. Mitotic activity is negligible. (1,3) Tumor cells are reactive to vimentin, smooth muscle actin, and muscle specific actin, and are nonreactive to desmin, S-100 protein, epithelial membrane antigen, and keratins. (3,4,8)

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COMMENT

This case presents an excellent opportunity to develop a differential diagnosis for buccal swellings in the oral cavity. Epithelial and mesenchymal lesions can produce soft tissue masses. The swellings may be developmental, inflammatory, of neoplastic origin, or represent oral manifestations of a systemic disease. The radiolucent appearance of this lesion mitigates it being a calcifying odontogenic tumor. During the development of differential diagnoses, some factors to consider include location of the lesion, consistency, and the presence or absence of pain. An important component in diagnosis is to remember that the most commonly occurring lesions are most often what you encounter. The use of vitality testing and periodontal evaluations along with radiographic surveys can eliminate lesions of periapical or periodontal origin. The focus can now be shifted to the more common developmental odontogenic or neoplastic entities. In this case, firm fibrotic lesions to consider include myofibroma, irritation fibroma, neurofibroma, angiofibroma, myofibromatosis, and fibrotic pyogenic granuloma.

Myofibromatosis is an admixture of myofibroblasts and fibroblasts. Lesions fall into 2 categories: superficial myofibromatosis with nodules confined to the subcutaneous and submucosal stroma with occasional involvement of skeletal muscle or bone; and generalized myofibromatosis with visceral lesions. (9) Myofibromatosis presents in the paraoral area as single or multiple submucosal nodules, usually in neonates and infants.

Traumatic fibroma may arise in any location and represents fibrous hyperplasia due to trauma. Traumatic fibroma may be clinically indistinguishable from true neoplasms, benign salivary tumors, or cysts. (10)

Odontogenic fibroma is a benign neoplasm that presents as a painless expansion of the cortical plates. (11) This tumor occurs as frequently in the maxilla as it does in the mandible. Root resorption or divergence is common.

Neurofibroma arises from the sheath cells of nerves and the mandible is the most common site for central nerve sheath neoplasms. (12) Expansion of the buccal plate is common with no associated pain. Paresthesia may or may not be present.

The pyogenic granuloma is a benign mass of exuberant granulation tissue produced after injury (or local infection) resulting in excess vascular tissue. (10) The mass may become fibrous over time. The treatment is conservative surgical removal with a slight chance of recurrence.

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Myofibroma is a rare benign soft tissue neoplasm of contractile myoid cells with predilection for the head and neck. (5,9,13,14) It occurs over a wide age range but is usually seen in young adults, mean age 27.12 The most frequently affected areas are the cheeks, tongue, mandible, lips, palate, trunk, and extremities. (13) Myofibromatosis describes the multicentric and more aggressive form, usually seen in neonates and infants. (3) Solitary myofibromas are more common than the multicentric form (5) and typically present as a firm painless slow growing submucosal mass (7) which may exhibit rapid growth and can often spontaneously regress. (4,12,14) The radiographic appearance is nonspecific and may appear as a well-demarcated or ill-defined radiolucency, with or without calcifications. (15) Intraosseous tumors occur most commonly in the mandible. (2,14)

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REFERENCES

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(14.) Sugatani T, Inui M, Tagawa T, Seki Y, Mori A, Yoneda J. Myofibroma of the mandible. Clinicopathologic study and review of the literature. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1995;80(3):303-309.

(15.) Kempson RL, Fletcher CDM, Evans HL, Hen drickson MR, Sibley RK. Atlas of Tumor Pathology. Tumors of the Soft Tissues. Washington, DC: American Registry of Pathology, Armed Forces Institute of Pathology; 1998;64-67.

COL Collins T. Lyons, DC, USA

COL Preston Q. Welch, DC, USA

COL David C. Flint, DC, USA

Harold B. Snyder, DDS, MS

AUTHORS

COL Lyons is Chief, Periodontics and AEGD Mentor at the Fort Jackson Dental Activity, Fort Jackson, South Carolina.

When this article was written, COL Welch was Oral Pathologist at the Madigan Army Medical Center, Fort Lewis, Washington.

COL Flint is Oral Pathologist at the Walter Reed National Military Medical Center, Bethesda, Maryland.

Dr Snyder is in private practice in Frederick, Maryland.
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