Pulmonary colloid adenocarcinoma mimicking lung abscess with concurrent KRAS and TP53 mutations: a case report.

Background: Pulmonary colloid adenocarcinoma is a rare subtype of lung adenocarcinoma, representing fewer than 1% of all cases. Characterized by abundant extracellular mucin and sparse tumor cells, it frequently mimics infectious lung diseases, making preoperative diagnosis particularly challenging. Case presentation: We report the case of a 44-year-old woman who presented with fever, pleuritic chest pain, and dyspnea. Laboratory evaluation revealed leukocytosis, elevated C-reactive protein, and increased procalcitonin. Radiologic findings showed a large, septated cystic lesion measuring 11 cm in the right lower lobe, accompanied by lobar consolidation and a small pleural effusion, initially suspected to be a lung abscess. Despite the administration of antibiotics and attempted percutaneous drainage, symptoms persisted. Consequently, surgical resection was performed, and histopathology confirmed colloid adenocarcinoma with visceral pleural invasion but no nodal metastasis. The patient subsequently received adjuvant chemotherapy and has remained recurrence-free for over 3 years. Targeted next-generation sequencing identified co-occurring KRAS and TP53 mutations along with a truncating AXIN2 variant, suggesting concurrent activation of the RAS/MAPK and Wnt/β-catenin pathways. Conclusion: Pulmonary colloid adenocarcinoma can clinically and radiologically mimic a lung abscess. Failure to respond to standard antibiotic therapy and drainage should prompt consideration of an underlying malignancy. Surgical resection is essential for both definitive diagnosis and treatment.