['The role of TNFalpha in cancer is complex with both pro-tumourigenic and anti-tumourigenic roles proposed. We hypothesised that anatomical microlocalisation is critical for its function.', 'This study used immunohistochemistry to investigate the expression of TNFalpha in the tumour islets and stroma with respect to survival in 133 patients with surgically resected NSCLC.', 'TNFalpha expression was increased in the tumour islets of patients with above median survival (AMS) compared to those with below median survival (BMS)(p = 0.006), but similar in the stroma of both groups. Increasing tumour islet TNFalpha density was a favorable independent prognostic indicator (p = 0.048) while stromal TNFalpha density was an independent predictor of reduced survival (p = 0.007). Patients with high TNFalpha expression (upper tertile) had a significantly higher 5-year survival compared to patients in the lower tertile (43% versus 22%, p = 0.01). In patients with AMS, 100% of TNFalpha+ cells were macrophages and mast cells, compared to only 28% in the islets and 50% in the stroma of BMS patients (p < 0.001).'] Does tumour necrosis factor-alpha expression in tumour islets confer a survival advantage in non-small cell lung cancer?