Elastin in pulmonary pathology: relevance in tumors with lepidic or papillary appearance. A comprehensive understanding from a morphological viewpoint

Elastin and collagen are the main components of the lung connective tissue network and together provide the lung with elasticity and tensile strength. In pulmonary pathology elastin stain is used to a variable extent in different countries. These uses include evaluation of the pleura in staging and distinction of invasion from collapse of alveoli after surgery (iatrogenic collapse). In the latter, elastin is used to highlight distorted but pre-existing alveolar architecture from true invasion. In addition to variable use and experience, the interpretation of elastin in some adenocarcinomas leads to interpretative differences between collapsed lepidic patterns and true papillary patterns. This review aims to summarize the existing data on the use of elastin in pulmonary pathology, based on literature data and morphological characteristics. The effect of iatrogenic collapse and interpretation of elastin in pulmonary adenocarcinomas is discussed in detail, especially for the distinction between lepidic patterns and papillary carcinoma.