Teaching Case

A 64-year-old female presented with severe sleep apnoea that did not significantly improve with continuous positive airway pressure (CPAP) treatment. The patient did not report any other significant symptoms such as dysphagia, foreign body sensation in the throat or dyspnoea.

Computed tomography (CT) showed a large well-defined fat density lesion in the retropharyngeal space extending craniocaudally from the level of the anterior arch of C1 to the level of C7. The lesion exerted mass effect on the posterior oropharynx and hypopharynx and displaced laterally the right carotid space.

On magnetic resonance imaging (MRI), the lesion showed hyperintensity on T1-weighted and T2-weighted sequences, with signal loss on fat suppression sequences. The lesion did not invade adjacent spaces, and no enhancing septa or nodular components were seen after gadolinium administration.

Lipomas are benign tumours of mesenchymal origin composed of mature adipocytes, and they usually occur in the torso and extremities. Even though they are the most common soft tissue tumours, lipomas of the head and neck region are less common, and lipomas of the retropharyngeal space are even rarer [1,2].

They can be associated with specific syndromes of lipomatosis of the head and neck, such as Madelung’s disease, also known as Multiple Symmetrical Lipomatosis. This syndrome usually involves the head, anterior and posterior neck, typically occurs in males in their 3rd to 7th decade of life and has a strong association with alcohol abuse [3].

Because they are slow-growing tumours and are not easily accessible to physical examination, retropharyngeal lipomas only cause symptoms when they are large and compress surrounding structures. The most common symptoms associated with retropharyngeal lipomas are dysphagia, snoring, and obstructive sleep apnoea [4].

According to the World Health Organization's classification of soft tissue tumours, benign adipocytic tumours include lipomas, chondroid lipomas, angiolipomas, and spindle cell lipomas, among others. It is important to make the distinction between benign adipocytic tumours from more aggressive variants such as atypical pleomorphic lipomatous tumour and well-differentiated liposarcoma [5].

The diagnosis relies on different imaging techniques, such as CT and MRI, since a final diagnosis cannot be achieved on physical examination alone, and these are also useful for surgical planning [6].

On CT, lipomas present as well-defined hypoattenuating lesions with fat density (usually ranging from -50 to -150 Hounsfield units). Even though they cannot be differentiated from well-differentiated liposarcomas from these characteristics alone, they do not show infiltrative behaviour or enhancing soft tissue components [7].

MRI can better delineate the tumour and its relationship with surrounding structures. Lipomas show hyperintensity on T1-weighted and T2-weighted imaging and show loss of signal intensity with fat suppression techniques. Lipomas should not be enhanced after gadolinium administration as that would be a concerning feature [8].

The definite diagnosis is made by histopathologic examination.

Surgery is usually reserved for symptomatic cases and can be achieved by a transoral or transcervical approach. The transoral approach is preferred due to lower morbidity, with the transcervical approach reserved for large lipomas or when they extend laterally to the carotid sheath [3].

The patient was proposed for surgery but declined.

Written informed patient consent for publication has been obtained.