Intrathoracic fibrolipomas are extremely rare, and to the best of our knowledge, only three such cases have been previously reported in the English literature. One of these was associated with the posterior mediastinum, and two were associated with the parietal pleura [1, 2, 5].
Lipomas and their variants exhibit attenuation of fat of approximately − 100 HU on CT images. Moreover, magnetic resonance imaging (MRI), particularly with fat saturation, is helpful for assessing the lipomatous nature of the tumor. In addition, MRI aids in distinguishing between lipomas and well-differentiated liposarcomas based on margins, signal homogeneity, and septa or nodules . PET imaging may also be an objective and useful modality for preoperatively evaluating tumors involving adipose tissue. In the present case, the tumor was considered to be a benign lipomatous tumor, rather than a malignant liposarcoma, following confirmation using CT and PET images. However, completely excluding liposarcoma can be difficult. For preoperative diagnosis, additional MRIs may provide information regarding tumor descriptions; moreover, histological evaluation using core needle biopsy could be performed. Conversely, the differentiation of various histological types of lipomatous tumors is not easy, particularly when limited tissue is available for assessment. Therefore, in the present case, we decided to completely resect the lesion, without obtaining an MRI scan or performing core needle biopsy.
In the present case, intraoperative, frozen-section analysis revealed that the tumor was rich in fibrous components and demonstrated no malignancy. Generally, benign lipomas and liposarcomas can be distinguished depending on the presence of hyperchromatic nuclei; however, the identification of atypical stromal cells is not always easy. Thus, establishing a differential diagnosis using only intraoperative frozen-section analysis is difficult for pathologists. Because the differentiation of lipomas and liposarcomas is essential for proper patient management, it is important to conduct a detailed examination of the whole resected specimen.
The lipomatous tumors exhibit varied clinical course. The first-line treatment for these tumors involves surgical resection. The prognosis is favorable for benign lipomas and well-differentiated liposarcomas after complete resection. However, high-grade tumors such as pleomorphic liposarcomas may develop distant metastases.
Fibrolipomas present clinical characteristics similar to those of lipomas. Intrathoracic fibrolipomas are usually asymptomatic; however, the development of tumor causes the compression of surrounding organs, resulting in a shortness of breath and dysphagia . In the three previously reported cases of intrathoracic fibrolipomas, the tumors were relatively large (> 8 cm) but asymptomatic. Fibrolipomas are commonly capsulated, and those originating from the parietal pleura are usually pedunculated, which facilitates an easy separation of fibrolipomas from surrounding organs. In previously reported cases, standard thoracotomies were necessary to excise the tumors owing to their large sizes.
In the present case, the tumor was asymptomatic and was relatively small upon when first detected. Therefore, successfully resecting the tumor using complete thoracoscopic surgery was possible. Although fibrolipomas are histologically benign, careful observation and follow-up are essential owing to the possibility of recurrence .