Fibromatosis

Aggressive fibromatosis describes the formation of a soft-tissue mass (desmoid tumor) that can be classified pathologically at any point along the spectrum between benign and malignant. (1) These locally aggressive tumors are uncommon, accounting for fewer than 3% of all soft-tissue tumors. (2) Only 10 to 15% of these lesions occur in the head and neck. (1)

A 35-year-old woman presented with a history of a painless mass on the right side of her neck that had grown gradually over a period of months. The epicenter of the mass was at the level of the oropharynx. There was no evidence of any other primary malignant tumor. Computed tomography (CT) demonstrated a large soft-tissue mass that was isointense to muscle with minimal enhancement (figure 1). The mass was located lateral to the carotid space. Magnetic resonance imaging (MRI) showed a relatively well-marginated mass with marked enhancement (figure 2). Surgical excision of the mass revealed that it was a desmoid tumor.

[FIGURES 1-2 OMITTED]

Imaging findings reported in the literature describe a poorly marginated transspatial enhancing mass in the soft tissue of the extracranial head and neck that arises from the musculoaponeurotic structures. (3) The most common locations are the supraclavicular and masticator spaces. There is a broad range of interaction with the surrounding soft tissues. A less aggressive variety of these tumors appears as well-circumscribed masses. The more aggressive tumors appear to invade the adjacent muscle and bone. CT findings may be nonspecific. Findings on T1-weighted MRI demonstrate that these masses are of intermediate to low intensity in relation to adjacent muscle. On T2-weighted MRI, these masses may be heterogeneous in signal intensity. On postcontrast T1-weighted MRI, the enhancement may be moderate to marked, with irregular margins in the more malignant lesions. The differential diagnosis on imaging includes rhabdomyosarcoma, fibrosarcoma, lymphoma, and metastatic disease. (3)

References

(1.) Sanders KW, Fowler MR, Milner J, et al. Aggressive fibromatosis of the parapharyngeal space: Two cases and treatment recommendations. Ear Nose Throat J 2004;83:262, 264, 266.

(2). Plukker JT, van Oort I, Vermey A, et al. Aggressive fibromatosis (non-familial desmoid tumour): Therapeutic problems and the role of adjuvant radiotherapy. Br J Surg 1995;82:510-14.

(3.) Harnsberger HR, Hudgins PA, Wiggins RH III, et al. Aggressive fibromatosis. In: Harnsberger HR, Hudgins PA, Wiggins RH III, et al, eds. Diagnostic Imaging: Head and Neck. 1st ed. Salt Lake City: Amirsys, 2004:IV 24.

From the Department of Radiology, Louisiana State University Health Sciences Center, New Orleans.

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