A survey of the literature dealing with this particular phase of the cancer problem indicates that surprisingly little investigation has been made in this direction. It was Borst's opinion1 that the parenchyma of the epithelioma is often retarded by the new connective tissue development roundabout. According to Unna's rule,2 "The cellular infiltration of the cutis increases with the activity of the epithelial growth, when the epithelial margin is the seat of marked proliferation."
Concerning the presence of plasma cells, Aschoff, Ribbert and Borst say little. In 1891, Jadassohn3 referred to the "encircling wall of plasma cells and leukocytes," and Unna,2 describing the plasmoma of Paget's disease, characterizes it as "a bulwark of defense against cancer invasion." Reviewing a series of twenty-eight cases of epithelioma, Unna reports that fourteen contained many plasma cells, variously distributed, but often encircling the epithelioma. He also found numerous mast cells, usually