A
sarcoma (from the Greek
sarx meaning "flesh") is a
cancer that arises from transformed
cells of
mesenchymal origin. Thus,
malignant tumors made of
cancellous bone,
cartilage,
fat,
muscle,
vascular, or
hematopoietic tissues are, by definition, considered sarcomas. This is in contrast to a malignant tumor originating from
epithelial cells, which are termed
carcinoma. Human sarcomas are quite rare. Common malignancies, such as
breast,
colon, and
lung cancer, are almost always carcinoma.