Pulmonary <i>In Situ</i> Adenocarcinoma with Mosaic Paving Pattern

CONTEXT: Adenocarcinoma already comprises half the cases of lung cancer. Its insidious clinical evolution contributes to the fact that, in absolute numbers, lung tumor is the cancer with the highest mortality in the world. When still in situ, the adenocarcinoma is even quieter, making its typical presentation on the computerized tomography of an irregular semisolid nodule smaller than 3.0 cm. It is often diagnosed in a finding of examination in an asymptomatic patient. The prevalence of in situ adenocarcinoma (ISA) is less than 5% of pulmonary malignancies and its radiological presentation with a diffuse mosaic paving pattern is even more unusual, mimicking other conditions more frequent to this finding. CASE REPORT: We describe the case of a 44-year-old male patient with a history of chronic smoking admitted to the emergency room at a referral hospital in São Paulo on 12/16/2016 with a complaint of progressive dyspnea associated with dry cough for 3 months, intermittent fever and weight loss of 8 kg in 2 months. A chest X-ray and computed tomography showed discrete focal points of peribroncovascular consolidation, predominantly central, areas with frosted glass attenuation associated with smooth thickening of the interlobular septa, sometimes interspersed with areas of preserved parenchyma, giving an aspect of “crazing paving” with diffuse distribution by the pulmonary parenchyma. The patient underwent a biopsy with the anatomicopathological diagnosis of primary Adenocarcinoma in situ of the lung. CONCLUSION: We emphasize that the “crazing paving” of adenocarcinoma in situ pulmonary should be considered and known by the radiologist, because although isolated it is a rare condition, its early distrust in cases of atypical evolution of the most common injuries can avoid a diagnosis in phases more advanced and higher mortality.