Teaching Case

A 42-year-old asymptomatic female patient was referred for a chest radiograph and HRCT due to a suspected systemic sclerosis.

The PA projection of chest X-ray (Fig. 1a) shows a widening of the mediastinal para-oesophageal line, in the lower left part; the LL projection (Fig. 1b) shows a bulging of the retrocardiac space, with a presence of opacity with density of soft tissues.
The Chest CT (Fig. 2) demonstrates the absence of lung involvement, but it shows in the middle and lower mediastinum, predominant on the left side and disposed around the oesophagus and aorta, the presence of tissue with a density of -100 / -110 HU and subtle hyperdense septa in its interior.
A double MDC Oesophagus X-ray (Fig. 3) performed for screening of systemic sclerosis, shows a hypotonic and hypokinetic oesophagus in absence of compression phenomena.
The Chest MR (Fig. 4, 5, 6) confirms the presence of intrathoracic lipoma extended from the plane passing through pulmonary trunk to the diaphragmatic hiatus. The mass is encapsulated, well-clotted by the mediastinal organs.

Lipomas are a benign tumours that originate from fatty tissue. [1, 3]. They can appear anywhere in the body; thoracic lipomas are rare. [1, 2, 3]

Generally, the majority of lipomas become apparent in patients at 40 to 60 years of age, and they tend to be more common in obese persons. [6]

The lipomas that involve the thorax can be divided into two groups:
- Subcutaneous: usually appears in the upper back, neck, and shoulder regions.
- Deeply seated: intrathoracic (or mediastinal) lipoma. This group can be classified into two classes:
• pure intrathoracic: located completely within the thoracic cavity
• mediastinal lipoma that have intra-and/or extra-thoracic lesions. In particular:
- cervico-mediastinal type which extends to the neck
- transmural type which penetrates the chest wall. [1, 2, 3, 6]

Deeply seated intrathoracic lipomas usually tend to have a big size and their detection is often late and incidental, e.g. while the patient is performing routine examinations or imaging investigations for mild symptoms [1]. Generally they are characterised by slow growth; for this reason, usually they are asymptomatic. [1, 5] The symptoms are often due to mass effect and depend on the site and size of the lesion. [5 and 6] The patient can have: dysphagia, dyspnoea, dry cough, jugular distention, and cardiac arrhythmias or even death. [4, 5, 6]

At a X-ray examination, a lipoma can appear like a well-defined rounded nodul/mass that presents soft tissue density. [3, 6]
On a Chest CT, lipomas show homogeneous fat attenuation of approximately (- 50 to -150 HU). [2, 4, 6]
MRI is useful to describe the extent of the mass, and the relationship between this and the adjoining organs. [3, 4] Also, it can be of help to identify the fatty nature of the lesion [4]; it presents a high signal intensity on both T1- and T2-weighted images. [6]
Usually radiologic investigations are useful for diagnosis, but can’t exclude the malignancy. [2]

In general, surgical resection is necessary to:
-prevent:
o increasing in size
o infiltrating development
o local recurrence
o malignant degeneration
- avoid a mass effect on adjacent structures and/or alleviate symptoms
- pathologic examinations and verification of the diagnosis [1, 2, 6]

MR is performed to exclude a possible suspicious mass not seen in CT; in this way the liposarcoma is excluded.
The clinicians decide to avoid a biopsy or a surgical resection because the patient is asymptomatic and prefers a clinical follow-up.