Mast cells and the nodal sinus reaction in breast cancer

Mast cell counts in the sinuses of axillary nodes from breast cancer patients are shown to vary with the type of sinus reaction present. Few scattered mast cells were found in association with sinus histiocytosis. A mixed reaction, in which fewer histiocytes were present and more round cells, was accompanied by a significant increase in mast cell count, which in sinus catarrh showed a decrease. The possible rôle of sinus mast cells in relation to tumour spread is discussed.