Desmoid tumors arise from musculoaponeurotic stromal elements and are locally invasive, deep-seated fibrotic tumors. They are destructive of surrounding tissue, with a high rate of recurrence, but are not known to have the capacity to metastasize. Desmoid tumors have two general classifications, intraabdominal and extraabdominal. This distinction is significant in determining proper clinical management. Extraabdominal tumors are predominantly sporadic, and often can be effectively treated with local resection; systemic treatment is generally reserved for refractory tumors. Conversely, intraabdominal desmoid fibromatosis, for example those seen with familial adenomatous polyposis and Gardner syndrome, are often diffusely infiltrative and surgically unresectable; systemic therapy is considered first-line treatment of intraabdominal desmoids. Extraabdominal tumors in the paranasal sinus are extremely rare; to the best of our knowledge only six cases have been reported in the literature 123456 (Table 1).

An otherwise healthy seven-year-old male presented with a six month history of chronic sinus congestion and halitosis. He was initially treated for atopy and bacterial sinusitis with no resolution of symptoms. Suspicion was raised of a foreign body in the nose and ENT consultation was ordered. Prior to endoscopic removal of the foreign body, computed tomography (CT) of the head was performed.

CT revealed a large expansile mass, 4 cm in greatest dimension, expanding and eroding the walls of the sphenoid sinus and the posterior ethmoid air cells. Because the mass extended cephalad into the base of the skull, magnetic resonance imaging (MRI) was performed. MRI found no evidence of meningeal involvement or brain parenchymal invasion and the major intracranial arteries appeared intact. The right optic nerve was displaced but without evidence of impingement.

The patient underwent functional endoscopic sinus surgery with biopsy of the lesion. Histological analysis revealed a cellular myofibroblastic neoplasm suggestive of extraabdominal desmoid fibromatosis (Figures 1, 2). Surgical resection was performed and histological analysis confirmed the diagnosis. Surgical margins were positive. Because of the rarity of this tumor, particularly in the paranasal sinuses of a child, immunohistochemical examination was performed. The tumor showed focal positivity for SMA and multifocal nuclear positivity for beta catenin; desmin, S-100, and CD34 were negative.

Desmoid tumors are rare, accounting for approximately 0.03% of all neoplasms, and less than 3% of all soft tissue tumors. The estimated incidence in the general population is 2-4/1,000,000/year, which in the US translates to approximately 900 new tumors annually 7. Individuals between the ages of 15 and 60 are most often affected; desmoid tumors are rare in the young and in the elderly. They are slightly more common in women than in men 89, and there is no significant racial or ethnic distribution. Desmoids tend to be large bulky tumors that locally infiltrate adjacent tissue structures. Histologically, they are characterized by small bundles of spindle cells in an abundant fibrous stroma. The fibroblasts have a propensity to concentrate at the periphery of the lesion, and the cellularity is low. There are usually few mitotic figures and necrosis is absent. The etiology of desmoid tumors is unknown. However, the identification of clonal chromosomal changes in a significant fraction of cases supports the neoplastic nature of these tumors 10, and emerging evidence implicates dysregulated wound healing in the pathogenesis of these and other fibroblastic lesions. Trisomy 8 and 20 as nonrandom clonal chromosomal changes, particularly trisomy 8, occur in at least 30% of sporadic desmoid tumors 11121314. Although the clinical relevance of these genetic abnormalities is unclear, these genetic insults appear to be associated with a higher risk of recurrence 12.

Because of their locally infiltrative nature, desmoid tumors are traditionally treated by local resection with wide surgical margins when significant morbidity can be avoided 1516. Considering the potential toxicity and morbidity associated with local and systemic therapy in children, complete surgical excision is the treatment of choice for aggressive juvenile fibromatosis. Because these are benign tumors with a high rate of recurrence, surgeons must balance the need to obtain tumor-free margins while at the same time using function-preserving approaches to minimize major functional and cosmetic sequelae. The available data are conflicting with regard to the importance of complete resection. Buitendijk et al. 17 reported that, of 187 published cases of juvenile fibromatosis, the single greatest determinant of tumor recurrence was incomplete resection. In another evaluation of 63 pediatric patients, the only factor associated with an increased rate of recurrence-free survival was negative surgical margins (70% versus 15% with positive margins) 18. In contrast, several authors report that the risk of recurrence is independent of margin status 19202122232425. In one of the largest series of 203 patients undergoing surgery for either primary or recurrent desmoid tumors, margins were microscopically positive in 57 and negative in 146 21. As expected, the disease-free survival rate was significantly better in patients with primary disease (76% versus 59% at 10 years), but it was not significantly worse for those with microscopically positive versus negative margins at primary surgery (five year disease-free survival rate for those with positive and negative margins, 79% versus 82%; at 10 years, 74% versus 77%). In patients who undergo aggressive resection with wide margins recurrence rates remain at 23% to 39% 1526272829. When they recur, salvage therapy with radiation therapy (RT) and/or repeat excision is often successful. This data cast some doubt on the current dogma of aggressive pursuit of negative surgical margins in cases that may result in excessive morbidity 919. The uncertainty as to the importance of positive resection margins also spurs controversy with regard to the role of postoperative RT for patients with incompletely resected disease.

Desmoid fibromatosis are rare pediatric tumors, and the case reported here is one of only six published accounts of pediatric desmoid fibromatosis of the paranasal sinuses. Aggressive juvenile fibromatoses are a group of lesions with variable response to treatment; they are locally aggressive but have low metastatic potential. Current treatment ranges from traditional surgical resection to multidisciplinary approaches involving local radiation and/or systemic cytotoxic and cytostatic agents. However, surgical resection with wide margins remains the primary treatment for extraabdominal fibromatoses. Reports in the literature are conflicting as to the importance of obtaining tumor-free surgical margins; some retrospective analyses have found a significant decrease in recurrence rate with negative margins, while others have not. Based on these reports, the optimal treatment strategy for pediatric desmoids fibromatoses is patient-dependent, and clinical decisions must be made based upon tumor location, risk of surgical morbidity and risk of radiation-induced damage. Radiation therapy and cytotoxic chemotherapy in pediatric patients should be used in cases that are refractory to surgery and noncytotoxic systemic therapy due to the potential of growth disturbance, contracture, and the development of secondary malignancy.

CT: computed tomography; IFN-alpha: interferon alpha; MRI: magnetic resonance imaging; NSAID: non-steroidal anti-inflammatory drug; PDGFRA: platelet-derived growth factor receptor-alpha; RT: radiation therapy; SMA: smooth-muscle actin.

The authors declare that they have no competing interests.

SL, RE, and LH secured the case, conducted the literature review, and participated in the preparation of the manuscript. All authors read and approved the final manuscript.

Written informed consent was obtained from the patient's parents for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.