Abstract Introduction Adenocarcinoma of the lung is a common malignancy that may present with nonspecific respiratory symptoms and imaging findings resembling infectious pneumonia, often leading to delayed diagnosis. The lymphatic spread of tumor cells can generate diffuse infiltrates, closely mimicking infection both clinically and radiographically. This report describes a case where presumed pneumonia was ultimately diagnosed as lung adenocarcinoma with lymphangitic metastasis, emphasizing the importance of reconsidering the diagnosis early in non-resolving cases. Case Presentation A 72-year-old male with a remote history of a 7 mm right lower lobe pulmonary nodule (identified eight years prior), chronic obstructive pulmonary disease, alcohol and tobacco use, presented with progressive shortness of breath, fever, and productive cough. He exhibited hypoxemia requiring high-flow nasal cannula. There was no chest pain, hemoptysis, sick contacts, or recent travel. The patient was lost to follow-up due to loss of insurance and had declined further workup for prior imaging findings. Three months before admission, he had been treated with antibiotics and steroids for presumed community-acquired pneumonia without improvement. On presentation, laboratory studies revealed leukocytosis (WBC 19.8K, neutrophilic predominance). Blood cultures, respiratory viral panel, and urine antigens for Streptococcus pneumoniae and Legionella were negative. Chest X-ray demonstrated right-sided consolidation, and computed tomography showed extensive right lower lobe consolidation with air bronchograms. Empiric therapy with doxycycline and piperacillin-tazobactam was initiated. Bronchoscopy was not performed due to high oxygen requirements, and a CT-guided lung biopsy was pursued instead, revealing moderately differentiated adenocarcinoma with lymphangitic spread—a finding associated with aggressive disease and poor prognosis. Medical oncology promptly started carboplatin and pemetrexed. Despite chemotherapy initiation, the patient’s oxygen requirements worsened, and he ultimately succumbed to progressive respiratory failure. Discussion This case illustrates how lung adenocarcinoma, especially with lymphangitic spread, can closely mimic pneumonia, resulting in diagnostic delays. Persistent or progressive pulmonary infiltrates unresponsive to appropriate antimicrobial therapy warrant early tissue diagnosis to exclude malignancy. Regular surveillance and follow-up for incidentally noted pulmonary nodules are essential for timely intervention. Its is important to maintain a broad differential diagnosis in non-resolving pulmonary infiltrates to avoid missed opportunities for intervention. This abstract is funded by: n/a
Shah et al. (Fri,) studied this question.