Hemangioendothelioma is used to describe a group of vascular neoplasms that may be considered benign or malignant according to their activities. Six histopathological variants have been described: papillary intralymphatic angioendothelioma, retiform hemangioendothelioma, kaposiform hemangioendothelioma, EHE, pseudomyogenic hemangioendothelioma, and composite hemangioendothelioma. EHE is a relatively uncommon vascular endothelial tumor which is considered an intermediate vascular neoplasm between a benign hemangioma and a highly aggressive angiosarcoma. EHE can occur in soft tissues and various organs . Mediastinal location is very exceptional, and only few cases were reported [6–11]. As the most common primary neoplasms in the mediastinum were thymic and neruogenic tumors, the correct diagnosis of EHE is a great challenge.
Histologically, EHE is characterized by cords and nests epithelioid cells with intracytoplasmic vacuoles in a myxohyaline stroma. The formation of intracytoplasmic vacuole represents the primitive vascular differentiation of endothelial cells. Usually, the tumor cells are quite bland, showing light atypia. Infrequently, the tumor cells may be focally spindling, and very rarely, the scattered multinucleated osteoclast-like giant cells may be present within the tumor cells [11–15].
Our case showed extensive spindle-cell changes with scattered osteoclast-like giant cells. Histologically, the tumor was predominately composed of sheets of atypical spindle cells and scattered osteoclast-like giant cells. So, we firstly thought it might be a tumor complicated with multinucleated giant cells such as malignant fibrous histiocytoma. The presence of classic epithelioid cells with intracytoplasmic vacuoles in myxohyaline stroma and the positive expression of CD31 and CD34 can usually favor the correct diagnosis and rule out malignant fibrous histiocytoma . Usually, it is difficult for pathologists to consider the possibility of vascular tumors. If the specimen is limited,from fine-needle aspiration, or histologically lacks the classic patterns, the correct diagnosis may be a great challenge.
In addition, the differential diagnosis also includes some other tumors, which can possess osteoclast-like giant cells, such as giant cell tumor from bone or soft tissue, chondroblastoma, chondrosarcoma, osteosarcoma and dedifferentiated liposarcoma. Based on the histological structure and immunohistochemical staining, the correct diagnosis can be made. Moreover, some sarcomatoid carcinomas can present as extensive spindle cells with osteoclast-like giant cells. Thus, sarcomatoid carcinoma is also an important differential diagnosis. Particularly, in addition to the vascular markers such as UEA-1, factor VIII-related antigen, CD31 or CD34, EHE is also immunopositive for the epithelial marker CK , which may be a potential diagnostic pitfall. It is essential to use a panel of antibodies to make the correct diagnosis.
To date, the reported case with osteoclast-like giant cells is exceptional rare [11, 13–15]. The significance of osteoclast-like giant cells is still unclear. The osteoclast-like giant cells were only immunopositive for CD68, but negative for CD31 and CD34, indicating these cells may bejust reactive cells. And, further follow-up should be made to investigate its significance.
According to Mentzel et al.  and Weiss et al., , the majority of EHEs have a relatively better clinical course than highly aggressive angiosarcoma. However, if the tumor shows marked cellular atypia, mitotic activity (>1 mitosis per 10 HPF), necrosis and extensive spindling, it may have a more aggressive course . Deyrup et al. also reported that EHE tumor over 3.0 cm had poor prognosis . But, it is still unclear whether the presence of osteoclast-like giant cells is associated with prognosis. In this case, because of the extensive presence of atypical spindle cells and tumor size, we diagnosed it as a “high risk” EHE.
Treatment of EHE varies and depends on the site and extent of tumor involvement, site(s) of metastasis, and specific individual factors. Surgical resection, radiotherapy, and chemotherapy all have been used to treat these masses, although studies on survival have yet to be conducted to delineate various treatment regimens. Surgery is the preferred treatment as long as the entire tumor could be removed, since there’s little chance of growing back. If it’s impossible to remove the whole tumor surgically, or if there are multiple tumors in several locations, several medications will be commended to slow the growth of the tumor by interfering with abnormal cell growth, ie, anti-angiogenic agent, vincristine, interferon, Rapamycin, radiation and other treatments. The prognosis of EHE is not sound, almost a third of EHEs develop metastases in regional lymph nodes (at least 50% + of all metastatic cases) or in the lungs, liver or bones. Patients who develop metastases have a 50% five-year survival rate. In the current case, the mass has been fully removed by surgical resection, and the patient took adjuvant chemotherapy. Within 18-month follow-up, no recurrence was found.