Abstract Lung adenocarcinoma is the most common subtype of non-small cell lung cancer and a major cause of cancer-related mortality worldwide. Miliary pulmonary nodules are classically associated with infectious etiologies such as tuberculosis or fungal disease. However, in rare instances, they can represent metastatic spread of malignancy. Differentiating infectious from malignant causes is often challenging because of overlapping imaging features and the limited diagnostic yield of conventional biopsy techniques. Recent advances in transbronchial lung cryobiopsy offer higher diagnostic yield and larger tissue specimens, enabling improved histopathology and molecular testing. A 67-year-old man with stage IV lung adenocarcinoma, diagnosed four years earlier with right upper lobe adenocarcinoma, presented for evaluation of new diffuse miliary pulmonary nodules noted on surveillance chest computed tomography (CT). Initial disease involved a solitary metastatic bone lesion treated with radiation. He was asymptomatic with no signs of infection or systemic symptoms. CT imaging revealed innumerable sub-2 mm nodules with a miliary pattern, predominantly in the right lung, which were new compared to prior imaging three months earlier. Positron Emission Tomography (PET)-CT showed no fluorodeoxyglucose (FDG) uptake within these nodules. Given his marijuana use with non-sterile water pipe exposure, infectious etiologies were initially a concern. Comprehensive microbiologic stains and cultures were negative. Bronchoscopy with bronchoalveolar lavage and transbronchial lung cryobiopsy (TBLC) was performed. Histopathology revealed metastatic adenocarcinoma with tumor cells proliferating along alveolar septa in a lepidic pattern and TTF-1 positivity, confirming recurrent malignancy. The patient was started on systemic chemotherapy and immunotherapy with stable disease 18 months later, though the miliary pattern persisted on follow-up imaging. This case underscores that miliary pulmonary nodules, although often infectious, may represent metastatic lung adenocarcinoma; a rare and diagnostically challenging presentation. Diagnosis of lung diseases relies on tissue sampling via bronchoscopy, CT-guided biopsy, or surgery. TBLC is a relatively new method using a cryoprobe to freeze and extract lung tissue, yielding larger, better-preserved specimens than forceps biopsy. For lung nodules, cryobiopsy achieves greater diagnostic accuracy than conventional biopsies by providing sufficient tissue for molecular and histopathologic analysis. Although rare, cryobiopsy can diagnose miliary pulmonary nodules from metastatic adenocarcinoma, a rare atypical presentation often indistinguishable from infection, offering a less invasive, high-yield alternative to surgery while improving diagnostic accuracy and patient management. This abstract is funded by: None
Arora et al. (Fri,) studied this question.