Figure 3. Heamotoxylin and eosin stained micrographs of the tumour-host interface of a formalin-fixed specimen from human squamous cell carcinoma of the head and neck. An acellular gap between the tumour and normal tissue edges is identified (arrows), consistent with the predictions of the mathematical model (cf. Figure 2). Note the dying normal cells just beyond this acellular gap (arrowheads) presumably due to acid-induced apoptosis.