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Introduction

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The upper aerodigestive tract is home to several rather generalized fibrous and myofibromatous proliferative disorders. Broadly called fibromatosis or desmoplastic fibroma, such proliferations typically behave in a benign manner but sometimes are locally aggressive and may have an alarming, infiltrative histopathologic appearance. The more aggressive lesions are frequently called juvenile aggressive fibromatoses or extra-abdominal desmoids. Myofibromatosis is an admixture of smooth muscle cells and fibroblasts within a fibrous stroma; it is discussed elsewhere in this book, as are generalized fibromatosis of gingival tissues and gingival fibrous hyperplasia, special forms of fibrous proliferation.


Clinical Features

Soft tissue fibromatosis of the oral region is rare but is, after the vascular developmental lesions, the most common of the congenital masses of the oral soft tissues. It occurs primarily in children and young adults but may be seen in middle-aged individuals as well. There is no gender predilection.

This lesion presents as a broad-based, firm, sometimes lobulated, painless, slowly enlarging mass with normal coloration (Figures 1 & 2). The speed of enlargement is variable and should not be used as a reliable predictor of aggressive future behavior.  Fibromatosis usually develops adjacent to the mandible, where underlying bone may be eroded or destroyed by "invasion." Lesions average 3-4 cm. in size at diagnosis, but lesions as large as 9 cm. have been reported, as have multiple lesions in the same patient. Larger lesions may develop secondary surface lobulation.


Pathology and Differential Diagnosis

Fibromatosis is characterized by a proliferation of spindle-shaped, somewhat primitive mesenchymal cells arranged in streaming fascicles (Figures 3 & 4).  Reticulin stains and Masson trichrome stain will confirm the collagenic nature of the stroma. Thin-walled vascular spaces are invariably present but not in large numbers. The lesional periphery is poorly demarcated from surrounding tissues, appearing often to be infiltrating those tissues. Erosion of underlying bone or actual destruction of bone may be seen. The degree of cellularity is variable, with some cases demonstrating moderate numbers of lesional cells in a background stroma of abundant mature collagen, and others showing minimal stroma with large numbers of active mesenchymal cells. In both types, cellularity is most evident at the periphery of the tumor. Hyperchromatic and pleomorphic nuclei are seldom seen. Occasional normal appearing mitotic figures may be found, but should not exceed 4 mitoses per high-power field. The presence of dysplastic mesenchymal cells should make the pathologist suspicious for fibrosarcoma, malignant fibrous histiocytoma, or fibroblastic osteosarcoma (if attached to bone).

Occasional fibromatoses infiltrating striated muscle will induce atrophy, degeneration and regeneration of muscle cells, resulting in the presence of osteoclast-like multinucleated giant cells and imparting a giant cell lesion appearance.


Treatment and Prognosis

  Oral fibromatosis is treated by wide excision, including a thin margin of adjacent normal tissues. It has a locally aggressive behavior with a recurrence rate of more than 20%. This rate is similar to the rate for lesions of the sinonasal area, but is far below the rate for lesions of the neck or other extra-abdominal locations (40-70%). Recurrences are treated by re-excision. Severe, multicentric lesions with visceral involvement are much more serious and may lead to respiratory distress or diarrhea. The oral lesions are, however, usually of minimal consequence in such cases.

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References (Chronologic Order)

Note: General references can be found by clicking on that topic to the left.

Larsson A, Bjorlin G. Aggressive fibrous lesions of the oral cavity. J Oral Pathol 1976; 5:241-251.

Vally IM, Altini M. Fibromatoses of the oral and paraoral soft tissues and jaws. Review of the literature and report of 12 new cases. Oral Surg Oral Med Oral Pathol 1990; 69:191-198.

Coffin CM, Dehner LP. Fibroblastic-myofibroblastic tumors in children and adolescents: a clinicopathologic study of 108 examples in 103 patients.. Ped Pathol 1991; 11:559-588.

Thompson DH, et al. Juvenile aggressive fibromatosis: report of three cases and review of the literature. Ear Nose Throat J 1991; 70:462-468.

Fowler CB, Hartman KS, Brannon RB. Fibromatosis of the oral and paraoral region. Oral Surg Oral Med Oral Pathol 1994; 77:373-386.

Plaited BEC, Balm TJM, Loftus BM, et al. Fibromatosis of the head and neck. Clin Otolaryngol 1995; 20:103-108.

Fisher C. Fibromatosis and fibrosarcoma in infancy and childhood. Europ J Ca 1996; 32A:2094-2100.

Gnepp DR, Henley J, Weiss S, Heffner D. Desmoid fibromatosis of the sinonasal tract and nasopharynx a clinicopathological study of 25 cases. Cancer 1996; 78:2572-2579.


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