Miliary Intrapulmonary Carcinomatosis: A Rare Phenotype with an EGFR Silver Lining in a Young Never-Smoker – A Case Report

A miliary pulmonary nodular pattern is classically associated with disseminated infectious diseases; however, reliance on this assumption leads to diagnostic anchoring and delay in recognition of noninfectious etiologies. Miliary intrapulmonary carcinomatosis (MIPC) is a rare but highly aggressive manifestation of lung adenocarcinoma with a miliary nodular pattern. We present a rare case of MIPC in a young never-smoker whose progressive clinical decline eventually led to a diagnosis of epidermal growth factor receptor (EGFR)-mutated lung adenocarcinoma. This case highlights the diagnostic challenge posed by the radiographic overlap between infectious and malignant causes of miliary disease and underscores the importance of early tissue diagnosis when clinical features are atypical. MIPC has a strong association with EGFR mutations and may represent a radiographic phenotype suggestive of EGFR-mutated lung adenocarcinoma. Early molecular testing and initiation of EGFR-targeted tyrosine kinase inhibitors (TKIs) significantly improves clinical outcomes and survival, even in advanced disease and across racial groups.