A Rare Tumor of Mediastinum in Child; Giant Mediastinal Lipoma
Lipomas are benign mesenchymal tumors originating from fat tissue. Mediastinal lipomas are very rare, constitute 1.6% – 2.3% of all primary mediastinal tumors and most commonly anterior mediastinal placement. It is often asymptomatic and is detected incidentally on radiographs taken. The symptoms that he creates depend on the pressure he has on the surrounding organs. If symptoms are asymptomatic, follow-up is sufficient, but complete excision is needed. We aimed to present the imaging findings of asymptomatic a giant mediastinal lipoma that we have been following for 3 years.
Lipomas are benign mesenchymal tumors originating from fat tissue. Mediastinal lipomas are most commonly located in the anterior mediastinum and constitute 1.6% to 2.3% of all primary mediastinal tumors . Unlike subcutaneous lipomas, which are frequently seen in large numbers, mediastinal lipomas are a single lesion. It is asymptomatic and can be quite large at the time of diagnosis. It is usually found incidentally on chest radiography or computed tomography (CT) taken for another cause . The symptoms it creates depend on the pressure made from the neighboring structure (heart, lungs, vascular structure) . The excision is indicated when the tumor causes pain or when the neighboring structures put the function at risk due to pressure. In this article, we aimed to present the imaging findings of a giant lipoma entity that was detected incidentally and was followed up asymptomatically for 3 years in the thyroid gland adjacent to the anterior mediastinum.
A 13-year-old male patient was referred to our clinic upon detection of a mediastinal mass on chest X-ray. The patient had no complaints. There was no feature on her resume. There was no abnormality in physical examination and laboratory values. On the chest X-ray, on the left mediastinum, a smooth contour lesion of 14 x 5 cm was observed in the heart and soft tissues with a relatively radiolucent appearance (Figure 1). Magnetic resonance imaging (MRI) examination was performed on the mediastinum in terms of diagnosis and differential diagnosis. MRI examination revealed a hyperintense lesion on the T1-weighted starting from the inferior part of the thyroid gland, filling the anterior mediastinum with the left weighted, surrounding the vascular structures and massless effect, suppressed on the fat-suppressed images and non-enhancing lesion (Figure 2a, b, c). Giant mediastinal lipoma was considered with the present imaging findings. Biopsy or excision was not needed because the imaging findings of the lesion were typical and the patient had no complaints. There was no difference in lesion size and appearance on the control MRI examination performed 3 years later (Figure 3a, b, c). The patient has been followed up for 3 years by our annual MRI follow-ups in our clinic.
We presented a giant mediastinal lipoma with typical imaging findings extending from the thyroid gland adjacent to the anterior mediastinum in the neck region incidentally detected in our case. Clinically, lipomas are very common and frequently present in the subcutaneous regions of the body. Mediastinal lipomas are rare. The separation from normal fat tissue is made by the surrounding fibrous capsule . They grow very slowly over the years . Larger than 10 cm in size or greater than 1000 g in any plane take the name giant lipom . They are usually seen in the elderly and are very rare in children.
Although the etiology of lipomas is not completely known, genetic, endocrine, and traumatic factors are the most common cause of the disease. The uncontrolled growth mechanism of lipomas is not clear. Blunt trauma is one of the possible causes. After blunt trauma, fibrous tissue rupture may cause proliferation of fatty tissue. In some cases lipomas are associated with various syndromes such as Gardner’s syndrome, Madelung’s disease and Dercum’s disease [1,5].
Symptoms depend on the pressure effect on the peripheral organs, and the most common symptoms are swallowing difficulty, respiratory distress, cardiac arrhythmia, phrenic and spinal nerve paralysis, vena cava superior syndrome and Horner’s syndrome .
MRI findings are quite typical. Mediastinal lipomas usually appear as a capsular, homogenous fat mass. They show high signal intensity on T1- and T2-weighted images, suppressed in fat-suppressed images [6,7]. When cases are symptomatic, fine needle aspiration cytology (FNAC) may be required to differentiate with good differentiation liposarcoma in the preoperative period . There is no need for treatment in asymptomatic cases. Completely resection is necessary if malfunction occurs in neighboring organs due to tumor. During our 3-year follow-up period, no symptoms developed and there was no change in imaging characteristics .
As a result, the importance of imaging methods for mediastinal lipomas is great. We think that in asymptomatic cases with typical imaging features, MRI can safely be followed without any need for surgery or biopsy.
Conflicts of Interest: The authors have no conflicts of interest to declare.
Informed Consent: Informed consent was obtained from the patient and patient’s family for publication of this manuscript and any accompanying images.
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Figure 1. Chest x-ray show that, there is a smooth contour on the left side of the anterior mediasten, a relatively radiolucent lesion compared to the heart and soft tissues (arrow)
Figure 2a, b, c : Coronal T2-weighted MR image (a) show that starting from the neck filling the anterior mediastinum with the left weighted hyperintense lesion, axial fat-suppressed MR image (b) show that fat content of the lesion is suppressed and axial contrast-enhanced T1-weighted MRI image (c) show that lesion not enhanced
Figure 3a, b, c : Coronal T2-weighted image (a), axial fat-suppressed MR image (b) and coronal contrast-enhanced T1-weighted MRI image (c) show that no difference in lesion size and appearance for 2 years later