Abstract Introduction Pulmonary mucinous adenocarcinoma (PMA) is an uncommon lung adenocarcinoma subtype composed of columnar or goblet cells producing abundant mucin. Accounting for 2–5% of cases, it often mimics pneumonia radiographically, delaying diagnosis. Because screening uptake and molecular testing remain limited among Hispanic adults, this entity may present at advanced stages. We report a case of PMA causing acute airway obstruction and respiratory failure in a Hispanic woman, illustrating diagnostic and health-equity challenges. Case Presentation A 66-year-old Hispanic and chronic smoker woman with dyslipidemia presented with progressive dyspnea, dry cough, and 6-kg unintentional weight loss over three months. Examination revealed digital clubbing and decreased right-sided breath sounds. Arterial blood gas confirmed hypoxemic respiratory failure. Chest radiograph suggested pneumonia, but CT imaging demonstrated a 6.4 × 6.0 × 5.2 cm mass nearly occluding the right main bronchus with post-obstructive atelectasis (Figure 1). Laboratory studies were notable only for leukocytosis (14.1 K/µL). Flexible bronchoscopy revealed a friable, mucin-coated endobronchial mass. Biopsy showed tall columnar cells with intracytoplasmic mucin and extracellular mucin pools. Immunohistochemistry was CK7+, MUC5AC+, TTF-1−, Napsin A−, confirming invasive mucinous adenocarcinoma. A second bronchoscopy achieved partial mechanical debulking for palliation. Given the advanced, unresectable disease and poor performance status, the patient elected hospice care. Discussion PMA differs molecularly and clinically from non-mucinous adenocarcinomas. KRAS mutations—especially G12D and G12V—predominate, while NRG1 or ERBB2 fusions represent actionable targets. The FDA approval of zenocutuzumab (2024) for NRG1-positive NSCLC highlights the value of next-generation sequencing in this variant. Radiographically, PMA presents with dense consolidation, ground-glass opacities, or air bronchograms, often interpreted as infection. Endobronchial obstruction, though rare, can precipitate acute respiratory failure, and bronchoscopic debulking provides symptomatic relief. Lung cancer in Hispanic/Latina women remains under-detected due to lower participation in low-dose CT screening, limited insurance coverage, and language barriers. Consequently, they present more often with late-stage disease and receive less molecular testing. Our patient’s presentation underscores both a diagnostic pitfall and a persistent disparity affecting early detection.ConclusionPulmonary mucinous adenocarcinoma should be suspected in cases of nonresolving “pneumonia” or mucus-filled endobronchial lesions. Early bronchoscopy with tissue sampling and molecular profiling is critical to identify targetable alterations such as NRG1 fusions. Improving access to screening and precision diagnostics among Hispanic populations is essential to achieve equitable lung-cancer outcomes. This abstract is funded by: None
Gines et al. (Fri,) studied this question.
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