Abstract

The aim of this review is to explain why the term ‘desquamative interstitial pneumonia’ (DIP) should be discarded and replaced with modern terminology. Reason 1: DIP is a misnomer. Within a few years after the term was coined, it was shown that the airspace cells in DIP are macrophages not desquamated pneumocytes. Reason 2: As a result of overly simplistic and poorly defined histologic criteria, DIP is currently a mixed bag of smoking-related diseases and unrelated processes in never-smokers. Reason 3: DIP obfuscates the modern concept that smoking causes some forms of parenchymal lung disease. Despite the fact that >80% of cases of DIP are caused by smoking, it is currently classified as a ‘smoking-related idiopathic interstitial pneumonia’, an oxymoron. Reason 4: The premise that the presence of numerous macrophages within airspaces defines an entity creates problematic histologic overlap with other lung diseases that may feature prominent airspace macrophages. Reason 5: DIP is outdated. It was coined in 1965, when many entities in interstitial lung disease had not been described, smoking-related interstitial lung disease was an unknown concept, computed tomograms of the chest had not been introduced and immunohistochemistry was unavailable. We suggest a way forward, which includes eliminating the term DIP and separating smoking-related lung abnormalities (including accumulation of pigmented airspace macrophages) from cases characterised by numerous non-pigmented macrophages in never-smokers. The laudable goal of smoking cessation is not served well by muddying the relationship between smoking and lung disease with inaccurate, outdated terminology.