Background
Lipofibroadenoma (LFA), a thymic tumor, was classified into “rare thymomas” in the WHO classification [
1]. Until now, one and only case of LFA was reported in the English literature [
2], in which a 62-year old man was suffered from dyspnea, dizziness and pure red cell aplasia. The tumor was found in the anterior mediastinum by Chest X-ray scan and diagnosed as LFA with thymoma type B1. Here we report another case of LFA, which is not accompanied with any type of thymoma. The clinical and pathological features are presented.
Discussion
LFA is an unusual thymic tumor, and the clinical and pathological features are still unclear. Until now, only one case has been reported, and the clinical information is showed in table
1. The patient was a 62-year old man accompanied with pure red cell aplasia, and the clinical presentations were dyspnea and dizziness. Histologically, the tumor was accompanied with B1-type thymoma. The present case is a 21-year old man without any symptom. The pure red cell aplasia was not found and the tumor was not associated with any type of thymoma. The primary site of the tumors were all located in the anterior mediastinum, and both patients were received thymectomy and all alive with no evidence of disease after surgery.
Table 1
Previously reported cases of lipofibroadenoma of the thymus
| 62 | M | AM | Dyspnea and dizziness | Yes | Yes, Accompanied with B1-type thymoma | thymectomy | NA | 80/ANED |
Present case | 21 | M | AM | No symptom | NO | NO | thymectomy | 10cm×6cm×4cm | 46/ANED |
Pathology is still the gold standard in the diagnosis of LFA, in which the classic histological features were with thymic epithelial cells arranged as crack structure under the background of fibrous tissue. Lymphocytes are infiltrated in the crack and fat cells are distributed as individual or groups. In rare case, thymic corpuscle could be found. As far as the present case is concerned, the typical morphological characteristics are observed under the low power. Epithelial cells were positive to AE1/AE3, CK19 and the lymphocytes were immunostained with CD3 and CD20, which were used to make the diagnosis of LFA.
The differential diagnosis of LFA in histology primarily separated into thymolipoma and fibroadenoma, which intraductal type composed of interstitial and epithelial component. Epithelial cells were arranged as crack under the fibrous element, and the lack of fat cells and thymic component could be helpful in the distinguishing diagnosis. Thymolipoma was an unusual thymoma, which could lead to myasthenia gravis and autoimmune dysfunction [
3]. Recent report suggested that thymolipoma origined from thymic true hyperplasia [
4]. Under the microscope, epithelial and fibrous components can not be observed in the thymolipoma, which was the important point distinguishing from LFA. In addition, the biomarkers of CD57, c-Jun, p73, Casp9, and N-ras are also useful in the differential diagnosis [
5,
6].
The treatment for the patient we presented was thymectomy, and the necessary follow-up examination among forty-six months disclosed there was no palindromic lesion. RJ
et al. had ever reported that COX-2 was expressed in all subtypes of thymomas and thymic carcinomas [
7], which indicated COX-2 might be another potential novel target beside in thymic tumor therapeutic areas.
In general, LFA was a rare and benign thymic tumor, which might not be related to pure red cell aplasia, and the tumor accompanied with or without any type of thymoma. Histological features and immunohistochemical staining played an important role in diagnosis and differential diagnosis, in which thymolipoma and fibroadenoma were primary differential diagnosis. Thymectomy was regarded as the best treatment. However, much more cases are needed for further research.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
QG designed the study, performed the histological evaluation, and drafted the manuscript. QG and YG participated histological diagnosis and revising the manuscript. ZQ was involved in literature search and preparing the material. MJ and WX participated in providing the clinical information of this case. All authors read and approved the final manuscript.