Angiosarcoma : Grading
Some angiosarcomas are well-differentiated (low-grade) and composed of innocuous-appearing anastomosing network of sinusoids lined by minimally atypical endothelium. The diagnosis in such cases is based on the infiltrative growth pattern rather than cytologic atypia. The poorly-differentiated angiosarcomas are composed of solid sheets of high-grade epithelioid or spindle cells and may resemble carcinomas or high-grade sarcomas. The presence of well-differentiated foci with anastomosing vascular channels can be helpful in arriving at the correct diagnosis. Breast angiosarcomas have been classified into grades I, II, and III; however, the clinical significance and their relevance to outcomes is not certain. A risk stratification scheme based on the presence of epithelioid features and necrosis has been proposed. High-risk tumors (with both features; shown in this image) have a 24% 3-yr survival rate. Low-risk histologic group of angiosarcomas lacks necrosis and epithelioid morphology and has a 77% 3-yr survival rate.