These hemangioendotheliomas have 2 growth phases: an initial rapid growth phase, which is followed by a period of spontaneous involution (usually within the first 12 to 18 months of life). Detection of the hemangioendothelioma within the first 6 months of life is attributed to the initial rapid growth during this time; however, the tumor has been detected with fetal ultrasonography. Histopathologically, there are 2 types of hepatic hemangioendotheliomas:
Type I: Hemagioendotheliomas of this type have multiple vascular channels that are formed by an immature endothelial lining with stromal separation from bile ductules. Type II: These hemangioendotheliomas have an appearance that is more disorganized and hypercellular, and there are no bile ductules.In children, distinguishing between a primary malignant liver tumor (hepatoblastoma) and a benign primary hepatic lesion (hemangioendothelioma) is crucial. The absence of urinary catecholamines supports the diagnosis of hemangioendothelioma. In patients with hemangioendotheliomas, elevations in α1-fetoprotein levels are milder than those found in patients with hepatoblastomas. Infantile hepatic hemangioendothelioma is strongly suggested by the presence of a vascular lesion on imaging studies. A complex, heterogeneous mass is often seen on ultrasonograms; a complex tumor that lacks central enhancement can be see on CT scans; and the vascular nature of the lesion along with dilation of the aorta proximal to the origin of the celiac artery and a decrease in the diameter distally, indicating significant shunting, is seen on angiograms. Because most hemangioendotheliomas in infants sponanteously involute and regress within the first 12 to 18 months of life, asymptomatic lesions are generally managed conservatively.
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
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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.