Metagenomic next-generation sequencing as an unconventional approach to warn of tumor cells in a patients with non-mucinous pneumonic-type lung adenocarcinoma: Case report

Rationale:Pneumonic-type lung cancer (PTLC) is a special type of lung cancer with cough and expectoration as the main clinical symptoms and inflammatory signals as the main imaging manifestations. PTLC can be easily misdiagnosed as pneumonia, and the diagnosis and treatment are always delayed. Metagenomic next-generation sequencing (mNGS), as an emerging and effective method to identify occult pathogens, has been gradually adopted by clinicians. Patient concerns:A 58-year-old woman with recurrent cough and expectoration was admitted to hospital on January 12th, 2022. She reported that she was diagnosed with pneumonia half a month ago, after treatment with expectorant and antibiotics for 5 days, the symptoms were relieved. However, the symptoms worsened again 10 days after stopping the drugs. On the current presentation, she denied exposure to patients with infection of COVID-19, smoking history, night sweats, weight loss, rash, joint pain, fever, and shortness of breath. Diagnoses:The patient was diagnosed with non-mucinous pneumonic-type lung adenocarcinoma according to the clinical symptoms, changes of CT scans after treatment and cytopathology examinations. Interventions and outcomes:The patient was initially diagnosed with pulmonary infection according to computerized tomography (CT) scan. Expectorant and antibiotics used. However, the symptoms worsened again 10 days after stopping the drugs. On her return visit, the CT scan did not showed obvious consolidation absorption and was similar to the previous imaging findings. mNGS was performed to detect the occult pathogens. None pathogen was detected, however, 39 copy number variations were found in Human Chromosomal Instability Analysis of mNGS indicating the presence of tumor cells. The cytopathology findings confirmed the presence of lung adenocarcinoma (non-mucinous adenocarcinoma). She was treated with targeted antitumor drugs, and the CT scan after 20 days of targeted antitumor therapy showed obvious absorption of the lesions. Lessons:mNGS may have potential value to screen tumor cells in bronchoalveolar lavage fluid of patients with PTLC, especially in the patients whose samples in bronchioli cannot be collected using existing sampling tools.