Pharyngeal desmoid-type fibromatosis in a pediatric patient with Gardner's syndrome

Clinical History

A 6-year-old male with a personal history of Gardner's syndrome and foot and occipital muscle desmoid tumour resection presented to the emergency department with a clinical history of progressive dysphonia and dysphagia. In fibro-laryngoscopy, an oropharyngeal solid mass compressing the airway was observed.

Imaging Findings

A US examination was performed which demonstrated a well-defined soft tissue mass, heterogeneous but predominantly hypoechoic. At spectral doppler analysis it showed an arterial waveform.

CT showed a homogeneous attenuation oropharyngeal tumour with a diffuse moderate enhancement after intravenous iodinated contrast media administration.

MRI depicted a rounded, well defined oropharyngeal mass, with intermediate signal intensity on T1-weighted images and hyperintense signal on T2-weighted and STIR images, with moderate paramagnetic contrast uptake. It was located on the left submucosal oropharyngeal space, in contact with the left palatine and lingual tonsil and extending into the mouth's floor, hypopharynx and glottis, producing significant airway reduction.

Discussion

Desmoid tumours are rare tumours: the estimated incidence in the general population is 2-4/1.000.000 per year [2]. Most tumours are intra-abdominal or located on the abdominal wall (28-69 %)[1], the least common site is extra-abdominal. In addition, only 10% of the extra-abdominal tumours affect head and neck [1, 7]; therein lies the singularity of our case.
Their association with Gardner's syndrome is well established: 5-15% of desmoid tumours are associated with familial polyposis syndromes (APC mutation) such as Gardner's syndrome [5, 6].

They are also known as deep fibromatosis and/or aggressive fibromatosis and they are solid soft tissue tumours that proliferate from fibroblast mesenchymal cells. They are considered benign tumours but, in some cases, they have an aggressive evolution with adjacent structure involvement or local recurrences, even after a successful surgical resection [3].

Imaging examinations are useful to approach the diagnosis and to assess the extension, the mass effect, the relationship with adjacent structures and the surgical resection possibility. Although CT has a higher spatial resolution, the lack of ionizing radiation in MRI makes it especially suitable in infantile fibromatosis. Furthermore, MRI has a prognostic value since it has been shown that higher T2-weighted image intensity is associated with faster tumour growth [1].

Desmoid tumours are well circumscribed soft tissue lesions with an ovoid morphology. Their MRI signal characteristics are highly variable, depending on the predominant histological component (collagen, myxoid matrix or spindle cell) [4]. On T1-weighted images they are homogeneous and isointense or slightly hyperintense relative to muscle. On T2-weighted images they are usually heterogeneous: T2 hyperintensity translates fibroblast major component, while T2 hypointense areas translate hypocellularity or fibrosis [1]. After paramagnetic contrast agent administration they may show homogeneous or inhomogeneous enhancement versus no enhancement; the cell array explains this feature.
On CT they appear as well circumscribed soft tissue masses that show similar or mildly lower attenuation than the adjacent muscles, and slight enhancement after intravenous contrast administration.
On US images they are usually visualized as a hypoechoic lobulated mass that may infiltrate adjacent structures [2].

The first choice for treatment, especially when the tumours produce a mass effect, is the surgical resection, although radiotherapy and chemotherapy are also valid options.

Differential Diagnosis List

Final Diagnosis

Pharyngeal desmoid-type fibromatosis in a patient with Gardner's syndrome.

URL:	https://www.eurorad.org/case/13139
DOI:	10.1594/EURORAD/CASE.13139
ISSN:	1563-4086