The incidence of intraosseous hemangiomas increases with age, and most patients present after their fourth decade. The majority of patients are asymptomatic and women are affected twice as often as men. The most common sites are vertebral bodies (particularly in the thoracic segment) and the skull. Hemangiomas of the long bones (e.g., femur, humerus) and short tubular bones are less often encountered (26,57,71) (Fig. 6-1). Calvarial hemangiomas most commonly affect the frontal and parietal regions, and account for 20% of all intraosseous hemangiomas (74). These lesions arise in the diploic space and cause expansion that often involves the outer table to a great extent (79). Vertebral hemangiomas are very common and are observed in 11% of autopsied cases (50). They account for 28% of all skeletal hemangiomas (74). In this location the lesion typically involves the vertebral body, although it may extend into the lamina and, rarely, into the spinous process. Multiple vertebrae are sometimes affected.
The majority of vertebral hemangiomas are asymptomatic and are discovered incidentally. The pathologic fractures are rare (35). Symptoms occur when the affected vertebra expands in the direction of the spinal cord and causes compression (34,70,86). This neurologic complication is most commonly associated with lesions in the midthoracic spine (43,59,75). Another mechanism considered responsible for compression of the cord, although less frequently, is a fracture of the involved vertebral body and the formation of a soft tissue mass or hematoma (5,9).

On radiography, an osseous hemangioma in a long or short tubular bone is characterized by coarse striations or by multifocal lytic areas (60,93) (Fig. 6-2). Periosteal and cortical hemangiomas occur most commonly in the anterior tibial diaphysis. These lesions present as lytic, cortical erosions, occasionally accompanied by a periosteal reaction. In the vertebral body, hemangioma is characterized either by vertical striations or by multiloculated lytic foci (108). These appearances are referred to as a corduroy cloth pattern (Fig. 6-3A) or honeycomb pattern (Fig. 6-3B), respectively, and are considered virtually pathognomonic for this lesion (60). A calvarial hemangioma commonly appears as a lytic lesion that exhibits a radiating configuration of
thickened trabeculae, frequently arranged in a spoke-wheel or web-like pattern (79).

On computed tomography (CT) scan, vertebral hemangioma characteristically exhibits a pattern of multiple dots (often referred to as the “polka-dot” appearance), representing a cross-section of reinforced trabeculae (Fig. 6-4).

On magnetic resonance imaging (MRI), T1- and T2-weighted images usually reveal areas of a high-intensity signal that correspond to the vascular components, adipocytes, and interstitial edema (7,48,89,102) (Fig. 6-5). Areas of trabecular thickening exhibit a low signal intensity regardless of the pulse sequence used (79). Both CT and MRI obtained after intravenous administration of contrast material demonstrate a lesion enhancement (16,79,97,110).

On scintigraphy, the appearance of osseous hemangiomas ranges from photopenia (37,68) to a moderate increase in the uptake of radiopharmaceutical tracer (54,76,83). A recent study of single photon emission computed tomography (SPECT) imaging of vertebral hemangiomas and their correlation with MRI showed that in most cases hemangiomas exhibited normal uptake on planar images. SPECT images were also normal, particularly if the lesions were less than 3 cm in diameter. This study also showed a disparity between SPECT images and MRI: there was no correlation between MRI signal intensity changes and patterns of uptake on bone imaging (47). Arteriography of the hemangioma is rarely indicated (64).

On histologic examination, most hemangiomas consist of simple channels formed by an endothelium-lined basal membrane, morphologically identical with normal capillaries (Fig. 6-6). The lining endothelial cells are small, flat, uniform, and inconspicuous (50). Mitotic figures are rarely seen (21). Some or all of the vascular channels may be enlarged and may have a sinusoidal appearance, in which case the lesion is
referred to as cavernous type (Fig. 6-7), which incidentally is the most common, particularly in the calvaria (31). These lesions are composed of multiple large, thin-walled, dilated, blood-filled vascular spaces lined by endothelial cells (50). Endothelial cells of hemangiomas are consistently positive for CD31, CD34, and factor VIII–related antigen. It has recently been shown that the Fli-1 protein, a transcription factor involved not only in cell proliferation and tumorigenesis, e.g., in Ewing sarcoma/primitive neuroectodermal tumor (PNET) and lymphoma but also in formation of endothelial cells, including lymphatic endothelium, is expressed in the nucleus of normal endothelia and in endothelium-derived benign and malignant tumors (32,33). The hemangiomatous tissue often spreads between the preexisting bone trabeculae without distorting the original bone pattern (77).

The designation epithelioid hemangioma is used for vascular lesions that, unlike epithelioid hemangioendothelioma, are often arranged in a lobular fashion (66,98,99,107). According to O’Connell et al. (81,162), more than 50% of neoplastic vessels should be lined by epithelioid endothelial cells to establish the diagnosis. Well-formed vessels with open lumina contain enlarged eosinophilic endothelial cells, sometimes protruding into the lumen, with vesicular nuclei and occasionally with prominent nucleoli. However, overt nuclear atypia is absent. Typical mitoses can be detected, and cytoplasmic vacuoles may be seen. The stroma often contains an inflammatory infiltrate consisting of lymphocytes, eosinophils, and extravasated erythrocytes, but myxoid change or hyalinization is not present. However, the existence of an epithelioid hemangioma in bone similar to its soft tissue counterpart [which is also designated as angiolymphoid hyperplasia with eosinophilia or histiocytic hemangioma and which is regarded by some authors as being reactive (106)] has been questioned by others (25,30).

Patients with cystic angiomatosis usually present in the first three decades (79). There is 2:1 male-to-female predominance. The bones affected are most often those of the axial skeleton, as well as the femur, humerus, tibia, radius, and fibula (20,29,82) (Fig. 6-12). The bone- related symptoms are usually secondary to pathologic fractures through the cystic lesions. Most of the symptoms, however, are related to visceral involvement.

On radiography, the osseous lesions are usually osteolytic (Fig. 6-13), occasionally with a honeycomb appearance (Fig. 6-14). They are well defined and surrounded by a rim of sclerosis, and they vary in size (15,67) (Fig. 6-15). Although medullary involvement predominates, cortical invasion, osseous expansion, and periosteal reaction can occur (20). Rarely, sclerotic lesions may be present, and in these instances the condition may mimic osteoblastic metastases (51). On MRI the lesions usually show an intermediate signal intensity on T1-weighted images, and T2-weighted images with fat saturation show a mixture of high, intermediate, and low signal intensities (8).

Whether cystic angiomatosis is truly of blood vessel origin or of lymphatic derivation, or even represents a mixture of the two, is difficult to decide in a given case without IHC (50). On gross examination, the lesions of cystic angiomatosis resemble simple bone cysts (20). They consist of large cavities lined by a dull yellowish- gray membrane. Multiple communicating cysts, separated by thickened trabeculae of mature lamellar bone but without osteoblastic rimming (107), may also be present, producing a honeycomb appearance (87). In some cases osteoid and immature woven bone formation with rimming of active osteoblasts was reported (51). Histologically, the lesions are indistinguishable from those observed in capillary or cavernous hemangiomas (20). They contain multiple dilated, thin-walled vascular channels lined by flat endothelial cells (107).