Authors: Qin Jian , Di Xu , Min Liu , Bingzhu Hu , Chenghong Li

Abstract

Background: Bilateral multiple microcystic pulmonary lesions highly suspicious for metastasis are a rare radiological manifestation of lung adenocarcinoma, and have seldom been reported in young adults. Such lesions are easily misinterpreted as infectious or cystic lung diseases, potentially leading to delayed diagnosis and inappropriate management. We report a case of lung adenocarcinoma in a young welder with multifactorial risk factors who presented with bilateral multiple microcystic lesions and achieved a sustained response to osimertinib, aiming to improve recognition and timely management of this rare presentation.

Case presentation: A 35-year-old Chinese male welder presented with cough and blood-streaked sputum. Chest CT revealed a left lower lobe mass, mediastinal and left supraclavicular lymphadenopathy, and bilateral multiple microcystic lesions highly suspicious for metastasis. Despite anti-infective therapy, the pulmonary lesions persisted,and biopsy confirmed lung adenocarcinoma harboring an EGFR exon 19 deletion and a somatic TP53 co-mutation (PD-L1 TPS 10%). Osimertinib 80 mg daily achieved an ongoing partial response sustained at 9 months (−58.0%), with no significant adverse events.

Conclusions: This case highlights that bilateral multiple microcystic pulmonary lesions in a young patient with risk factors should raise suspicion of metastatic involvement from lung adenocarcinoma, prompting prompt pathological biopsy and genetic testing for timely diagnosis. In this patient, 9 months of osimertinib therapy achieved a sustained radiological response despite the concurrent TP53 mutation, suggesting that TP53 co-mutation did not preclude response in this patient, though this single case cannot be generalized.

Keywords: Young adult lung adenocarcinoma, metastasis, EGFR mutation, TP53, welder, targeted therapy, diagnostic challenge.