H. Yoshida et al.

657Fig. 5. The tumor consists of an accumulation of epithelioid cells forming nests in the growth
pattern with capillaries.
Fig. 6. Epithelioid cells showing abundant, eosinophilic cytoplasms with intracytoplasmic
vacuoles in various stages. The vascular channel is lined by large, plump tumor cellswith an aggregation of epithelioid cells outside.
Fig. 7. A fibromyxomatous stroma provides the background. The tumor cells (arrow) withvacuoles are arranged in a cord-like pattern.

90Epithelioid hemangioendothelioma of bone(1982). Epithelioid cells were accumulated in asmall area around the well-developed vascularchannel, which mimicked epithelioid hemangioma. Initially, EHE was proposed as one typeof vascular tumor with epithelioid cells including epithelioid hemangioma and epithelioid
angiosarcoma (Weiss et al., 1986). Epithelioid
hemangioma takes a benign clinical course, andis often mistaken for EHE (O’Connell et al.,
1993; Costa et al., 1996).
On plain radiographs, EHE appears solitarily or multicentrically, being purely lytic andexpansive with well-defined sclerotic borders,
as in benign vascular tumors (Tsuneyoshi et al.,1986). A coarse trabecular or honeycomb pattern is also common, but is rarely seen with adestruction pattern in the elderly (Bollinger etal., 1994), as Murphy et al. (1995) suggested.
In pulse sequences emphasizing a T1 contrast,bone tumors of a vascular origin show higher
intensities than skeletal muscles but lower thanfat; while in pulse sequences emphasizing a T2
contrast, signal intensities of bone tumors of avascular origin are significantly higher thanmuscles and fat (Boutin et al., 1996). In thepresent patient, signal intensity of the epiphyseal tumor of the right femur was close to that ofmuscles in T1-weighted images, whereas in T2weighted images, the intensity of the bonetumor was higher than that of muscles and withwell-defined margins.
EHE of the bone is generally categorized asa tumor of intermediate malignancy, slowly
growing with initial symptoms of pain and local
swelling. The clinical course of EHE of thebone depends on the degree of tumor malignancy, between an epithelioid hemangioma andan epithelioid angiosarcoma. It is most likelythat cancellous bone and cortical bone of thelower extremities are involved in EHE (Boutinet al., 1996). In EHE, lesions appear in a multicentric manner with an incidence of over 50%
and below 62%, particulary with a predilection
for bones of the lower extremities in one anatomic region (Bollinger et al., 1994). Bones of
the upper extremities, ribs, vertebrae and scapulae might be also involved in EHE, though theincidence would be lower (Tsuneyoshi et al.,1986). The multicentric type of EHE seems toshowed an abundant, eosinophilic cytoplasm
often with various-sized intracytoplasmic
vacuoles. The vascular channel was lined bylarge, plump tumor cells with an aggregation ofepithelioid cells outside (Fig. 6). Mitotic figures were scarcely observed in all 4 lesions. Afibromyxomatous stroma provided as the background in a large area taken from the tumors of
the patella and the fibula; in the fibromyxomatous stroma, the tumor cells with cytoplasmic vacuoles were arranged in a cord-likepattern (Fig. 7). Lymphocytic aggregation wasscarce in the stroma in a limited area. We performed immunohistochemical examination for
Factor VIII-related antigen and CD34 withmonoclonal antibodies, and detected strongly
positive reactions from the tumor cells including the vacuolating cells.

Discussion
The diagnostic term EHE was introduced for
unusual bone and soft-tissue tumors as acounterpart to vascular tumors, similar to thoseoriginating in the visceral organs with a 1%
incidence among all vascular tumors (Weissand Enzinger, 1982; Costa et al., 1996; Keeland Rosenberg, 1999). EHE is histologicallycharacterized by clusters of epithelioid cellswith various-sized vasculatures in the background of myxoid or fibrous stroma (Weiss andEnzinger, 1982; Maruyama et al., 1985;
Tsuneyoshi et al., 1986; Bollinger et al., 1994).
The epithelioid cells frequently show varioussized intracytoplasmic vacuoles, which mimicked a primitive vascular channel: positive reactions for Factor VIII-related antigen andCD34 and the presence of Weibel-Paladegranules proved that the epithelioid cells have a
distinctive nature among endothelial cells(Tsuneyoshi et al., 1986). In the present patient,
the tumors were initially observed to consist ofclusters of epithelioid cells which had vacuoles
compatible to the primitive blood vessels. The
cord-like arrangement of CD34-positive,
vacuolated cells was also recognized in thefibromyxoid matrix, which clearly indicated
EHE as mentioned by Weiss and Enzinger
91

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9 Maruyama N, Kumagai Y, Ishida Y, Sato H,
Sugano I, Nagao K, et al. Epithelioid haemangioendothelioma of the bone tissue. Virchows Arch
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10 Mirra JM, Kameda N. Myxoid angioblastomatosis of bones. A case report of a rare, multifocal
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11 Murphy MD, Fairbairn KJ, Parman LM, Baxter
KG, Parsa MB, Smith WS. From the archives ofthe AFIP. Musculoskeletal angiomatous lesions:radiologic-pathologic correlation. Radiographics
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12 Otis J, Hutter RVP, Foote FW Jr, Marcove RC,Stewart FW. Hemangioendothelioma of bone.
Surg Gynecol Obstet 1968;127:295–305.
13 O’Connell JX, Kattapuram SV, Mankin HJ, Bhan
AK, Rosenberg AE. Epithelioid hemangioma ofbone. A tumor often mistaken for low-grade
angiosarcoma or malignant hemangioendothelioma. Am J Surg Pathol 1993;17:610–617.
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take a benign course in affected regions, but ismore indolent than the solitary type (Kleer etal., 1996; Weiss et al., 1986). EHE associatedwith cutaneous and visceral organs gives a serious
influence on the clinical course (Kleer et al.,1994). Therefore, CT scanning and MR imaging
should be employed in predicting the prognosisof vascular tumors for a thorough examinationof a patient.
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Received March 10, 2000; accepted April 7, 2000
Corresponding author: Dr. Haruhiko Yoshida92