Papillary adenocarcinoma of lung is a variant where the major component shows papillary growth pattern, often with complex secondary and tertiary branching structure. The tumor cells are arranged in multiple layers around true fibrovascular cores. The papillary structures are often seen freely floating in the alveolar spaces. In contrast to papillary adenocarcinoma, the micropapillary variant shows delicate papillary tufts lacking fibrovascular cores. Papillary adenocarcinoma of the lung must also be distinguished from tangential sectioning of alveolar walls with lepidic adenocarcinoma. Sometimes, papillary and lepidic patterns coexist and merge imperceptibly with one another.