Formerly, any malignant growth, esp. one attended with
   great pain and ulceration, with cachexia and progressive emaciation. It
   was so called, perhaps, from the great veins which surround it,
   compared by the ancients to the claws of a crab. The term is now
   restricted to such a growth made up of aggregations of epithelial
   cells, either without support or embedded in the meshes of a trabecular
   framework.