Moving Through Genetic Alterations and PD-L1 Expression in High-Grade Fetal Adenocarcinoma of the Lung: A Case Report and Literature Review.

Background: Lung cancer, the most common malignancy in humans, can be classified into a wide range of subtypes and molecular variants. Fetal adenocarcinoma of the lung (FLAC) is an infrequent subtype of lung adenocarcinoma with distinct histological characteristics. However, its incidence is extremely low (0.1-0.5% of primary lung cancers), and its biological features remain poorly understood. In the era of immunotherapy and targeted therapy, characterizing the genetic alterations of FLAC is essential for developing personalized treatment strategies and improving patient outcomes. Here, we report the genetic alterations and PD-L1 expression in a patient with high-grade FLAC (H-FLAC) and review the relevant literature, This is one of the few reported cases describing PD-L1 expression and TP53 mutation status in H-FLAC. Case Manifestations: A 57-year-old man with a 30-year history of smoking presented to our hospital with persistent cough, sputum, and chest tightness for 30 years, which had worsened for 1 month. Computed tomography (CT) of the chest revealed an irregular nodule in the posterior segment of the upper lobe of the left lung. The patient underwent posterior resection of the left upper lung apex, and postoperative pathology suggested H-FLAC with a tumor stage of pT Conclusion: This case study provides an opportunity to better understand H-FLAC, whose genetic alterations have not been well characterized, and to identify valuable molecular markers for potential targeted therapies. We conducted gene sequencing and PD-L1 expression testing, which are helpful for H-FLAC research.