Abstract Introduction Lepidic predominant adenocarcinoma (LPA) of the lung, previously known as non-mucinous bronchioloalveolar carcinoma (BAC), is a rare subtype of non-small cell lung cancer originating from the alveolar epithelial cells. It is characterized by tumor cells spreading along alveolar walls without stromal, vascular, or pleural invasion. Clinically and radiographically, it can closely resemble pneumonia, often leading to misdiagnosis and treatment delays. We present a case highlighting the importance of early recognition and accurate diagnosis. Case Presentation A 67-year-old Caucasian woman with a history of COPD, chronic hypoxemic respiratory failure on 2L oxygen, previous smoking history, rheumatoid arthritis, and 9/11 attack-related inhalation injury, was admitted with a two-week history of progressively worsening dyspnea and cough, unresponsive to outpatient antibiotic therapy. She had three prior hospitalizations for presumed community-acquired pneumonia within six months, treated each time with antibiotics and steroids. She denied weight loss, anorexia, or hemoptysis. Given her recurrent non-resolving “pneumonias,” malignancy was suspected. A video-assisted thoracoscopic biopsy of the left upper lobe revealed a well-differentiated lepidic-predominant adenocarcinoma, with positive TTF-1 staining. Due to extensive bilateral disease, surgical intervention was deemed unsuitable. Molecular testing showed no mutations in EGFR exons 18-21, suggesting limited benefits from EGFR-targeted therapies. A PET scan was scheduled for staging, and next-generation sequencing along with serum-based circulating tumor DNA (ctDNA) testing was planned to guide further treatment. Discussion The term bronchioalveolar carcinoma (BAC) previously described lung cancers with lepidic growth, characterized by non-invasive spread along alveolar structures. However, the 2015 WHO classification replaced BAC with a new system based on histology and immunohistochemistry, categorizing lung adenocarcinomas into adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), and invasive adenocarcinoma. Lepidic growth is now considered part of invasive adenocarcinoma. It presents distinct clinical features compared to other non-small cell lung cancers, including a higher prevalence in females, Asians, minimal smoking history, and a relatively indolent course. Its clinical and radiographic similarity to pneumonia often leads to misdiagnosis and delayed treatment. Early tissue diagnosis via minimally invasive biopsy is essential, as imaging alone may be inconclusive, and PET scans often struggle to differentiate between infectious and malignant processes. This case underscores the need for heightened clinical suspicion and thorough evaluation in patients with recurrent pneumonia-like presentations, especially when typical infectious signs are absent. Early biopsy and molecular testing are crucial for accurate diagnosis and personalized treatment planning, which can significantly impact outcomes. This abstract is funded by: None
Baik et al. (Fri,) studied this question.