Tissue histamine levels and mast cell numbers in tumour-bearing mice

In C57BL/6 mice bearing the 3LL carcinoma and in C3H mice bearing the McC3 -1 fibrosarcoma (18th passage), the increase in skin histamine levels was correlated with the increase in mast cell number. The number of cells able to incorporate tritiated thymidine was proportional to the mast cell number. These results strengthen the notion that, in tumour-bearing rodents, the increase in tissue histamine is an active phenomenon.