If this is a YART I apologize, but I would like to ask if the original application of the word "cancer" (Latin for crab) to malignant growths is related to the pain that cancers can cause (perhaps like a crab inside that is causing pain with its pincers), or to the physical appearance of tumors with their spiculated, crab-like projections into the surrounding tissue? Does the OED have any comment on this?