PCNA and neoplasm: Cell proliferation was determined immunohistochemically by the number of proliferating cell nuclear antigen (PCNA)-positive cells in tumours, the extent of apoptosis was determined by counting the number of cells labelled by the in situ 3'-end labelling technique and tumour necrosis was estimated as the percentage of necrotic areas in haematoxylin--eosin-stained tissue sections.