A 51-year-old-man presented with symptoms and baseline investigations suggestive of an infective process. Most strikingly, there was a pronounced neutrophil predominant leucocytosis. Lack of a clinical and biochemical response to empirical antibiotic therapy, prompted imaging for a deep-seated infective process, incidentally uncovering a gastro-oesophageal junction tumour. Resection of the tumour was followed by rapid resolution of the leucocytosis. He remains in clinical remission since tumour resection and adjuvant chemotherapy. Cancer-associated leukemoid reactions in non-disseminated tumours are rare. The role of polymorphonuclear (PMN) leucocytes both in the peripheral blood and the tumour itself is discussed herein. There is increasing recognition of the importance of the non-cancer cellular components of the tumour microenvironment. Myeloid suppressor cells are a subset of PMN leucocytes which play a role in tumour progression.The role of these cells and granulocyte colony-stimulating factor is highlighted in this case.