Rare mass of the anterior mediastinum: Thymolipomas

Abstract

Thymolipoma is a rare benign neoplasm of the thymus containing both mature adipose tissue and thymic tissue. We report a case of a 34‐year‐οld man, presenting a mass of the anterior mediastinum, the radiology investigation and operatory piece diagnosed a thymolipoma.

This study highlights the clinical diagnostic and therapeutic features as well as the evolutionary characteristics of this entity.

Introduction

Thymolipoma is a rare benign neoplasm of the thymus containing both mature adipose tissue and thymic tissue. It represents 2%-9% of all thymic neoplasms [1]. Thymolipomas are slow-growing, benign tumors of the thymus. Mostly, they are asymptomatic. The diagnosis is strongly supported whenever a connection to the anterior superior mediastinum is demonstrated on imaging studies performed for a mass that contains fat and soft tissue or that is predominantly fatty.

Observation

The patient was a 34-year οld man, with4months’ histοry οf state II dyspnea, and chest pain without cough or hemoptysis. He was generally healthy. During the medical examination, the patient was conscious, afebrile, with tachypnea at 22 cycles per minute, normal heart rate (85 bpm), and normal blοοd pressure measured at 135/80 mm Hg. The physical examination revealed pulmonary dullness in the basal Hemi-left lung. Chest radiograph showed an opacity of the lower half of the left hemi thorax, silhouetting the left heart border and the left diaphragm (Fig. 1). The findings suggested a mass of anterior mediastinal location. No other pulmonary lesion was noted. There were no signs of pleural effusion. Thoracic contras-enhanced chest CT was performed and revealed a large well-defined heterogeneous mass with a predominance of fat density and focal areas of soft tissue density, which extended from the anterior mediastinum to the left diaphragm, displacing the lung superiorly (Figs. 23). There was no sign of pulmonary or adjacent tissue infiltration.

Fig. 1.

Chest radiograph showed an opacity of lower half of left hemithorax, silhouetting the left heart border and the left diaphragm

Fig. 2.

Unenhanced (A) and contrast-enhanced chest CT scan on the axial (B) and coronal (D,C) sections: revealed a large well-defined heterogeneous mass with predominance of fat attenuation values mingled with focal areas of soft tissue density, which extended from the anterior mediastinum to the left diaphragm, displacing the lung superiorly.

Fig.3.

On the control chest radiograph, there was a total disappearance of the opacity in the lower left hemithorax with ipsilateral costophrenic angle blunting.

The patient underwent total surgical excision of the mass. The histology study concluded a thymolipoma. On the control chest radiograph, there was a total disappearance of the opacity in the lower left hemithorax with ipsilateral costophrenic angle blunting (Fig. 3).

Discussion

Thymolipoma is a rare benign neoplasm of the thymus containing both mature adipose tissue and thymic tissue, accounting for 2-9% of all thymic tumors [2]. It affects both sexes equally, at any age with an age interval between 3 of 56 years and a peak at 33 years, and is located electively in the anterior mediastinum. These tumors usually demonstrate slow growth and can reach huge dimensions. Most are asymptomatic. Symptoms when present, are due to mass effect and compression; and include pain, cough or dyspnea [3]. They can be associated with some autoimmune diseases as myasthenia, systemic lupus erythematosus [4].

On chest radiographs, it presents as a mass that usually drapes over adjacent structures and can simulate cardiomegaly, pericardial masses, atelectasis or, pleural effusion. When small, thymolipomas can be limited to the anterior mediastinum. CT findings include a large, well-defined mass reflecting the encapsulation of this tumor. Thymolipomas are comprised predominantly (50-85%) of fat-attenuated tissue, representing the mature adipose component and focal and linear areas of soft tissue representing thymic tissue and fibrous septations [5].

The diagnostic confirmation is anatomopathological, indeed the macroscopic examination of the surgical specimen shows a well-limited tumor of soft consistency and appearance fat and lobulated at section slice [6]. The differential diagnosis includes fat-containing lesions such as teratomas, lipomas and liposarcoma, thymoliposarcomas, mediastinal lipomatosis, and diaphragmatic hernias [7,8]. Avidly enhancing, thick/nodular septa or evidence of local invasion are suggestive of malignancy moving towards the diagnosis of liposarcomas.

The treatment of thymolipomas consists of surgical removal. The surgical incision is usually by sternotomy; it allows an excellent exploration of the thymus.

Histopathological study is the only diagnostic tool that can rule out the benign or malignant nature of fatty masses in the mediastinum. The prognosis for thymolipoma is excellent as it does not infiltrate adjacent tissue and no malignant transformation has been reported [9].

Conclusion

Thymolipoma is a rare benign neoplasm of the fat mediastinal mass. Imagery has an important role in the detection of the fatty part, benign characteristics and the resectability evaluation. The diagnostic confirmation is anatomopathological.

Patient consent

Written informed consent was obtained from the patient for the publication of this case report.