155 Thymolipoma

Clinical Presentation

Asymptomatic 12-year-old boy

Radiologic Findings

PA (Fig. 155.1) and lateral (Fig. 155.2) chest radiographs demonstrate a right anterior-inferior mediastinal mass that conforms to the shape of the heart and mimics cardiomegaly. Note the lesion is not visible on the lateral chest radiograph (Fig. 155.2). Unenhanced chest CT (mediastinal window) (Fig. 155.3) shows a well-defined right juxtacardiac mass composed of soft-tissue elements intermixed with areas of fat. Note mild mass effect on the heart and visualization of intact adjacent subepicardial fat.

Diagnosis

Thymolipoma

Differential Diagnosis

• Morgagni Hernia

• Lipoma/Liposarcoma

• Mature Teratoma

Fig. 155.1

Fig. 155.2

Fig. 155.3

Fig. 155.4 Unenhanced chest CT (mediastinal window) of an obese 40-year-old man with mediastinal lipomatosis demonstrates fat attenuation tissue surrounding normal mediastinal structures without resultant mass effect.

Discussion

Background

Thymolipoma is a rare benign primary thymic neoplasm. Thymolipomas are characterized by their soft consistency and preferential growth in the inferior portion of the anterior mediastinum. These lesions may reach very large sizes in spite of minimal symptoms.

Etiology

The etiology of thymolipoma is unknown.

Clinical Findings

Patients with thymolipoma are usually young adults in the third decade of life, and men and women are equally affected. Patients may be entirely asymptomatic. Symptomatic patients present with complaints related to mass effect by large lesions and may complain of cough, dyspnea, and/or chest pain.