PUB151 The Intricate Management of the Epitheliod Haemangioendothelioma

Abstract

Epithelioid hemangioendothelioma (EH) is a very rare tumor with vascular origin and an epithelioid or histiocytoid appearance. It originates from medium-sized or large veins. In this case the neoplasm thought to be a teratoma and diagnosed postoperatively as an epithelioid hemangioendothelioma with metaplastic bone formation and extra medullary hematopoiesis. Pulmonary function tests as well as Alpha-fetoprotein and Beta hCG were normal. A decision for a robotic excision of the mediastinal mass was made. The procedure was uncomplicated/successful. Macroscopical examination revealed an anterior mediastinal mass covered by adipose tissue contained separate lymph nodes with no lymphovascular invasion, weighting 75g and measuring 72 x 50 x 38mm, with infiltrated areas and calcification. Microscopic examination showed fibro fatty tissue that was diffusely infiltrated by a cellular tumor. The tumor was characterized as uncapsuled, with poorly defined margins and with a predominant cell population of large epitheliod and spindled-shaped cells. These cells formed nodular areas and contained a glassy cytoplasm, which was in areas vacuolated and a prominent pseudonuclear inclusion. There was a low mitotic count and a low proliferative index (Ki67: <5%). Immunohistochemistry demonstrated that these cells expressed the vascular markers CD31 and CD34. Mixed with these cells some osteoclasts were observed as well as some metaplastic ossification. Some hematopoietic elements, hemosiderin laden macrophages, scattered hemosiderin as well as areas of sclerosis and occasional clusters of smooth muscle were also present. No tumor necrosis or mitotic figure was seen. Immunostains like SMA, desmin, myogenin, S100, Melan A, HMB45, AE1-AE3, MNF116, Cam5.2, chromogranin, synaptophysin, CD117, DOG1, EMA and GFAP were negative. Non-specific CD56 was present. Immunohistochemistry performed at RNOH showed that the tumor was diffusively positive for ERG. The pathological stage of the tumor was pT2bNxMx G1. Therapy of EH is difficult, because of the rarity. Surgery is a method that can be considered in unilateral single or multiple nodules. Interferon and chemotherapy containing the use of carboplatin and etoposide have been used in some cases. Bevasizumab, a monoclonal antibody against vascular endothelial factor (VEGF) has been also used in addition to chemotherapy in order to control the expansion of the tumor considering its vascular origin and the high expression of VEGF from it. Radiotherapy has been considered ineffective and has just been used to reduce the pain of bone involvement. Regular follow up with no active therapy has been used for asymptomatic patients with diffuse lesions.