Lung cancer caused by asbestos: What a reporting pathologist needs to know

Asbestos is a carcinogen that can cause lung cancer. The suspicion that a lung cancer diagnosis may be associated with exposure to asbestos has no bearing on treatment. However, attributing an individual's lung cancer to asbestos exposure has important medicolegal implications and may impact public health measures and policy. Simultaneous exposure(s) to other carcinogens (such as tobacco smoke, silica and many others) adds complexity while trying to answer the causation question. The Helsinki criteria were formulated to assist attributing lung cancer to previous asbestos exposure. Surrogate markers can be used and include signs of asbestosis and pleural plaques. The most widely used criterion for the presence of asbestosis is interstitial fibrosis in conjunction with 2 or more asbestos bodies/1 cm² tissue section by light microscopy. Identification of asbestos bodies ty light pr electron microscopy provides an important element for asbestos diagnosis. However, fibrosis may be subtle, and the distribution of asbestos bodies is not uniform throughout the lungs, some types of asbestos fibres have low biopersistence, and not all types of asbestos readily form asbestos bodies. Additional criteria require knowledge of exposure history, which is often unknown to pathologists, but reliance on morphology in isolation may lead to mis-classification of interstitial lung disease as idiopathic. While a smoking-related lung cancer signature has emerged, an asbestos-related lung cancer signature has not yet been identified. In this review we will discuss practice points for the surgical pathologist.