Thymic lipofibroadenoma of the anterior mediastinum: A rare case report

Lipofibroadenoma is an extremely rare thymic tumor, and the anterior mediastinum is the most common site. CASE SUMMARY: A 21-year-old male was admitted with fever without obvious cause for 2 months. After admission, the patient’s highest temperature was 38.3°C, accompanied by diarrhea. Physical examination showed coarse breath sounds in both lungs. Chest enhanced computed tomography (CT) showed a mass of mixed density shadow on the left side of the anterior mediastinum with a size of approximately 9.2 cm × 5 cm × 2.1 cm and a clear boundary mixed with a low fat density shadow. Mediastinal tumors were removed under general anesthesia by video-assisted thoracoscopic surgery. Macroscopically, a clear boundary was shown between the tumor and the remaining thymus. Microscopically, the tumor contained a large amount of mature adipose and fibrous tissue with scattered cord-like epithelial tissue and a small number of lymphocytes scattered in the stroma. The tumor lacked thymic bodies. The neoplastic epithelial cells were oval or polygonal and arranged in fissures, the nuclei were uniform in size and mild in shape, and mitosis was rare. Epithelial cells were positive for AE1/AE3 and CK19, lymphocytes were positive for CD3 and CD20, and fat and fibrous tissue were positive for S-100 and vimentin, respectively. The Ki67 labeling index was less than 5%. Based on histological features and immunophenotype, thymic lipofibroadenoma was diagnosed. The patient was followed up 1 year after the operation, and no recurrence or residual lesions were found on the X-ray re-examination. CONCLUSION: Lipofibroadenoma is a benign thymic tumor, and thymectomy is regarded as the best treatment. The biological behavior of thymic lipofibroadenoma is good, and the recurrence rate is low.