Lung cancer in a young adult mistaken for recurring pneumonia

What happened, in summary

A man in his 20s developed gradually worsening shortness of breath and a productive cough. He had a 10 pack-year smoking history, asthma, and occupational exposure to dust and metal-sanding particles. During 4 months, he was hospitalized 4 times and repeatedly treated for pneumonia.

The first CT showed dense consolidation in the right middle and lower lobes. Antibiotics gave only brief relief. He was later hospitalized with COVID-19 and low oxygen levels, then returned again with persistent cough and breathlessness. A bronchoscopy without biopsy found no cancer, and further antibiotics did not produce lasting improvement.

During the fourth admission, he was febrile, breathing rapidly, and needed supplemental oxygen. Imaging showed major progression, with near-complete filling of the right middle and lower lobes and enlarged mediastinal and hilar lymph nodes. Repeat bronchoscopy included several transbronchial biopsies. These finally showed well-differentiated lung adenocarcinoma.

PET imaging found extensive disease in chest lymph nodes but no spread outside the chest. The cancer was considered likely Stage IIIB. Tumor testing identified a KRAS G12C mutation. He was discharged with home oxygen. Two months later, he began carboplatin, pemetrexed, and pembrolizumab and had completed 2 cycles at the latest follow-up. He remained in active treatment under oncology follow-up.

Repeated infection testing and antibiotic courses did not explain the progressive lung changes. Obtaining actual lung tissue during repeat bronchoscopy finally changed the diagnosis from recurrent pneumonia to cancer. The persistent consolidation had masked the tumor for several months despite 4 hospital admissions.