Early-Stage High-Grade Fetal Lung Adenocarcinoma With KRAS Mutation: A Rare Presentation and Literature Review

IntroductionFetal lung adenocarcinoma is a rare malignant lung tumor, constituting about 0.1% to 0.5% of primary lung tumors. It is categorized into two types based on histopathological and clinical differences: low-grade and high-grade types. The primary distinction is the formation of morula bodies and β-catenin, P53 expression. High-grade fetal lung adenocarcinoma is more common in middle-aged to elderly men with heavy smoking history; it is highly malignant and often diagnosed with regional lymph node or distant metastasis. Recent literature mainly consists of case reports, focusing on advanced-stage high-grade type, with few reports concerning early-stage high-grade type.Case ReportThis article reviews the treatment journey of a rare early-stage high-grade fetal lung adenocarcinoma patient. The patient was a non-smoking elderly woman with no respiratory symptoms. A chest CT scan showed a nodule in the lower left lung, with normal tumor markers. Single-port thoracoscopic left lower lung wedge resection was performed, and intraoperative frozen pathology indicated invasive lung adenocarcinoma, leading to lobectomy and mediastinal lymphadenectomy. Postoperative pathology identified high-grade fetal lung adenocarcinoma, with pathological stage pT1bN0 IA2. We present the first report of early-stage high-grade fetal lung adenocarcinoma with KRAS mutation. At 17-month follow-up the patient remains disease-free without adjuvant therapy.ConclusionsDiagnosing fetal lung adenocarcinoma, an independent subtype of lung adenocarcinoma, relies on pathological evaluation, and the standard treatment is surgical resection. Since this disease is rare, early-stage high-grade fetal lung adenocarcinoma is even rarer, requiring more research to find the best treatment strategies.