Hemangioendothelioma of Bone
hemangioendothelioma (EHE) is a rare, well-differentiated endothelial
tumor with a wide spectrum of behavior. The term was designed to describe
tumors that had an appearance in between hemangiomas and sarcomas. Epithelioid
hemangioendothelioma has several synonyms: low grade anaplastic angiosarcoma,
cellular hemangioma, histiocytoid hemangioma and angioendothelioma. It
represents 1% of all vascular neoplasms and is locally aggressive.
Epithelioid hemangioendothelioma occurs in the calvarium,
spine, femur, tibia and feet of adults during the second or third decade.
Multiple lesion may be present, either in the same bone (particularly
in the tibia or fibula), in adjacent bones in the same limb, or in widely
separated bones. Nearby or distant soft tissues and skin may be
involved as well, and metastases to the lung (or simultaneous primary
lesions in the lung) have been reported in two cases. It is more
common in men than women and is found in the metaphysis or epiphysis.
Clinically, epithelioid hemangioendotheliomas presents with pain and swelling.
If present in the spine, a lesion may cause radicular symptoms or paraplegia.
On radiological examination, epithelioid hemangioendotheliomas
are expansive, osteolytic and poorly demarcated lesions. They have a distinctive
with a sclerotic margin. No periosteal reaction is present. Lesions
with particularly ill-defined margins and loss of trabeculae are considered
more aggressive. CT scan findings are noncontributory as they only reflect
soft-tissue density but lesions do enhance with contrast media.
MRI findings are also non-specific. The radiological differential includes
metastatic carcinoma, Ewing's sarcoma, telangiectatic osteosarcoma, lymphoma,
fibrous dysplasia and aneurysmal bone cyst.
On gross examination, epithelioid hemangioendotheliomas
are reddish-brown loculated masses with significant hemorrhage.
Microscopically, epithelioid hemangioendotheliomas
appear as irregular anastomosing vascular channels. The channels are lined
by plump endothelial cells without pleomorphism or mitotic activity. Both
the background stroma and the cells lining the vascular channels stain
positive for reticulum. The epithelioid histological subtype of epithelioid
hemangioendothelioma has epithelial like cells lining the vascular channels.
The spindle cell variant has spindle cells separating the vessels. Various
criteria are used to determine if the lesion is benign or malignant including
the number of mitoses, hyperchromatic nuclei, pleomorphism and nucleus
to cell ratio.
The treatment of epithelioid hemangioendothelioma
depends on the grade of the lesion. Benign appearing lesions may be treated
with currettage, or wide resection where possible. Wide resection or (rarely)
amputation are necessary for more aggressive tumors. The role of
radiation and chemotherapy is ill defined at this time. Epithelioid hemangioendotheliomas
may metastasize to bone and lung. Prognosis in these rare instances has
been variable but may be good.
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