This kind of mixed germ cell tumor may be known simply as a teratoma with elements of embryonal carcinoma or choriocarcinoma, or simply by ignoring the teratoma component and referring only to its malignant component:  embryonal carcinoma and/or choriocarcinoma. They can present in the anterior mediastinum. Cause
Some investigators suggest that this distribution arises as a consequence of abnormal migration of germ cells during embryogenesis. Others hypothesize a widespread distribution of germ cells to multiple sites during normal embryogenesis, with these cells conveying genetic information or providing regulatory functions at somatic sites.Extragonadal GCTs were thought initially to be isolated metastases from an undetected primary tumor in a gonad, but many germ cell tumors are now known to be  congenital and originate outside the gonads. The most notable of these is sacrococcygeal teratoma, the single most common tumor diagnosed in babies at birth.Of all anterior mediastinal tumors, 15–20% are GCTs of which about 50% are benign teratomas. Ovarian teratomas may be associated with anti-NMDA receptor encephalitis. Location
Despite their name, GCTs occur both within and outside the ovary and testis. They are found in:}

head
inside the cranium — pineal and suprasellar locations are most commonly reported
inside the mouth — a fairly common location for teratoma
neck
mediastinum — account for 1% to 5% of all germ cell neoplasms 
pelvis, particularly sacrococcygeal teratomaIn females, GCTs account for 30% of ovarian tumors, but only 1 to 3% of ovarian cancers in North America.
Hemangioendotheliomas are a family of vascular neoplasms of intermediate malignancy. Signs and symptoms
They have been described as masses that fall between a hemangioma and angiosarcoma. They are vascular tumors that commonly present with an enlarging mass and most commonly involve the lungs, liver, and musculoskeletal system, although many other body sites have been reported, including the head and neck, intestines, lymph nodes, pleura, retroperitoneum, heel, stomach. Cause
Possibly Bartonella spp bacteraemia

Diagnosis
Classification
Hemangioendotheliomas may be classified as:

Epithelioid hemangioendothelioma is an uncommon vascular tumor of intermediate malignancy that was first described by Steven Billings, Andrew Folpe, and Sharon Weiss in 2003. These tumors are so named because their histologic appearance resembles a proliferation of epithelioid cells, with polygonal shape and eosinophilic cytoplasm. Composite hemangioendothelioma is a low-grade angiosarcoma typically occurring in adults, although it has been described in infancy. : 601 
Spindle-cell hemangioendothelioma) is a vascular tumor that was first described in 1986 by Sharon Weiss, M.D., and commonly presents in a child or young adult who develops blue nodules of firm consistency on a distal extremity. : 599  These tumors were reclassified by Dr. Weiss in 1996 as "spindle cell hemangioma", rather than hemangioendothelioma, due to the excellent prognosis observed in a group of 78 patients. Retiform hemangioendothelioma (also known as a "Hobnail hemangioendothelioma") is a low-grade angiosarcoma, first described in 1994, presenting as a slow-growing exophytic mass, dermal plaque, or subcutaneous nodule. : 601 
Kaposiform hemangioendothelioma (also known as "Infantile kaposiform hemangioendothelioma") is an uncommon vascular tumor, first described by Niedt, Greco, et al.