Hemangioendothelioma is the term used to name those
vascular neoplasms that show a borderline
biological behavior, intermediate between entirely benign
hemangiomas and highly malignant
angiosarcomas. Although originally spindle cell
hemangioendothelioma was proposed as a specific clinicopathologic variant of
hemangioendothelioma, currently, it is considered as an entirely benign lesion, and thus, the name spindle cell
hemangioma seems to be the most accurate for this lesion. Authentic
hemangioendotheliomas involving the skin and soft tissues include papillary intralymphatic angioendothelioma (also known as Dabska
tumor), retiform
hemangioendothelioma,
kaposiform hemangioendothelioma,
epithelioid hemangioendothelioma, pseudomyogenic
hemangioendothelioma (also known as
epithelioid sarcoma-like
hemangioendothelioma), and composite
hemangioendothelioma. Each of these
neoplasms exhibit characteristic histopathologic features. The most characteristic finding of papillary intralymphatic
hemangioendothelioma consists of papillary tufts, with a central hyaline core lined by hobnail-like endothelial cells protruding into the lumina. Retiform
hemangioendothelioma is an infiltrative
neoplasm composed of elongated arborizing vessels, arranged in an anastomosing pattern that resembles that of the rete testis, and lined by a single layer of hobnail-like endothelial cells that protrude within the narrow lumina.
Kaposiform hemangioendothelioma is composed of several solid poorly circumscribed nodules, and each nodule is composed of a mixture of small capillaries and solid lobules of endothelial cells arranged in a glomeruloid pattern. A frequent finding consists of the presence of areas of lymphangiomatosis adjacent to the solid nodules.
Epithelioid hemangioendothelioma is composed of cords, strands, and solid aggregates of round, oval, and polygonal cells, with abundant pale eosinophilic cytoplasm, vesicular nuclei, and inconspicuous nucleoli, embedded in a fibromyxoid or sclerotic stroma. Many neoplastic cells exhibit prominent cytoplasmic vacuolization as an expression of primitive vascular differentiation. Pseudomyogenic
hemangioendothelioma is a poorly circumscribed, fascicular lesion with infiltrative borders composed of round or oval neoplastic cells, with vesicular nuclei and inconspicuous nucleoli, and ample homogeneous eosinophilic cytoplasm, giving them a rhabdomyoblastic appearance. Finally, composite
hemangioendothelioma is the term used to name locally aggressive
vascular neoplasms of low-grade
malignancy showing varying combinations of benign, low-grade malignant, and high-grade malignant vascular components. From the immunohistochemical point of view, proliferating cells of all
hemangioendotheliomas express a lymphatic endothelial cell immunophenotype. Most
hemangioendotheliomas are low-grade
vascular neoplasms, with a tendency to recur locally and a low metastatic potential, mostly to regional lymph nodes.
Epithelioid hemangioendothelioma, especially large lesions and those located in deep soft tissues, seems to have a more aggressive
biological behavior.