Vascular Sarcomas of Bone

Hannah D. Morgan

Vascular sarcomas of bone are extremely rare tumors for which the nomenclature is confusing, as there are a myriad of terms in the literature describing a spectrum of malignant vascular lesions. There are three major categories: hemangioendothelioma, a low-grade endothelial malignancy of bone; epithelioid hemangioendothelioma, a histologically distinct subgroup of endothelial malignancies; and angiosarcoma, high-grade vascular tumors of bone (Table 6.6-1). The differential diagnosis, treatment, and prognosis of these lesions vary according to the age of the patient, anatomic location(s) of disease, and histologic grade of each tumor.

Pathogenesis

Etiology

A potential predisposing factor is external-beam radiotherapy.

Table 6.6-1 Comparison of Vascular Sarcomas of Bone

Sarcoma Type	Age	Gender	Anatomic Distribution	Gross Appearance	Histologic Features	Other Details
Hemangioendothelioma	First through ninth decades	M > F (slightly)	Half involve lower extremity; any bone affected	Firm, friable, bloody	Well-formed vascular spaces (“staghorn spaces”) lined by plump endothelial cells. Intermixed with corded pattern mimicking carcinoma.	Multicentricity common; one third of cases multifocal
Epithelioid hemangioendothelioma	Second through eighth decades; peaks in second and third decades	M > F (slightly)	Femur most common; any bone affected	Firm, lobulated, tan	Corded, nested, or stranded pattern of plump endothelial cells with eosinophilic cytoplasm within hyalinized stroma (see Fig. 6.6-1). May form narrow vascular channels. Occasional cytoplasmic vacuoles (represent primitive blood vessel lumina). Signet ring=nlike appearance.
Angiosarcoma	Peaks in fourth decade	M > F (slightly)	Long tubular bones and spine most common; any bone affected	Firm, bloody	Less vasoformative than hemangioendotheliomas. Regions with vascular differentiation and plump malignant endothelial cells. Some areas may show epithelioid appearance.

Epidemiology

Extremely rare
- <1% of primary bone sarcomas
- Epithelioid sarcomas: <100 cases reported
If the tumor occurs after radiotherapy, the onset is typically several years following completion of the therapy.