The first treatments in this therapeutic class, known collectively as biological agents, were inhibitors of tumour necrosis factor-alpha (TNF-alpha).1–3 Tumour necrosis factor (TNF) plays a pivotal role in inflammation in RA4 and tumour necrosis factor inhibitors (TNFi) are highly effective in treating RA.5 From early in their development, there were concerns regarding the long-term safety of the TNFi with respect to malignancy, and in particular lymphoma.6, 7 The possible effects of TNF inhibition on lymphomagenesis are difficult to predict. The gene discussed is TNF; the disease is rheumatoid arthritis.