The cellular reaction during carcinogenesis: Variations in the numbers of mast cells, plasma cells and eosinophils.

Squamous carcinoma was produced in the hamster cheek pouch with D.M.B.A. The underlying cellular reaction of lymphocytes, plasma cells, mast cells and eosinophils was studied quantitatively during the various stages of development of the tumours. Between the early stage of hyperplasia and that of squamous carcinoma the eosinophils increased from 2 per cent to 17 per cent of all the cells present under the growths. There was a complementary fall in plasma cells as malignancy developed but the lymphocytes and mast cells remained at a fairly constant level. Possible reasons for these changes are discussed.