case_images: PMC9424904_01
case_images: Chest CT scans of the patient before and after savolitinib treatment. (A) The chest contrast-enhanced CT scan on July 1, 2021 demonstrates a 3.8 cm x 2.9 cm abnormal lung mass (white arrows) in the lobe of left lung. Enhanced signal was not detected inside the mass. Left hilar and subcarinal lymphadenopathy (red arrows) also were observed. (B) After 21 days of savolitinib therapy, the chest CT scan on August 13, 2021 showed the mass (red arrows) had shrunk to 2.6 cm x 2.2 cm, achieving a partial response (PR). The Left hilar and subcarinal lymph node (blue arrows) also shrank significantly, and the short diameter did not exceed 7 mm.
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case_images: Figure 1A ). Fluorine-18 fluorodeoxyglucose (F18-FDG) positron emission tomography (PET)/CT was performed to evaluate the whole-body situation on July 6, 2021. Additionally, the left hilar and subcarinal lymph node obviously shrank, and the short diameter did not exceed 7 mm ( Figure 1B ).
case_images: The 18F-FDG PET/CT examination was performed to evaluate the patient's tumor stage. The 18-FDG PET/CT revealed strong 18-FDG uptake in the left lung mass, as well as the left hilar and subcarinal lymph node, measuring up to 2.5 cm and 2.2 cm in short diameters, respectively, but there was no evidence of distant metastasis. See 
  Supplementary Material
   for a dynamic 3D visualization.
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case_images: The 18F-FDG PET/CT showed strong 18-FDG uptake in the left lung mass, as well as the left hilar and subcarinal lymph node, measuring up to 2.5 cm and 2.2 cm in short diameters, respectively, but there was no evidence of distant metastasis ( Figure 2  and  Supplementary Material ).
case_images: Operative and pathological findings. The pathological diagnosis was poorly differentiated lung adenocarcinoma (solid type) with the size of 2.2 cm x 2.0 cm x 1.2 cm, and the visceral pleura was not involved. No infiltration of cancer cells was detected in the bronchus cutting edges. Pulmonary hilar lymph node (-, 0/5). Immunohistochemistry outcomes were presented as: HE (A), TTF-1 (+) (B), NapsinA (+) (C), CK7 (+) (D), CK5/6 (-), CK (pan) (+), and Ki-67 (+, about 50%).
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case_images: The pulmonary hilar lymph node was negative (0/5) ( Figure 3 ).
case_images: Timeline of diagnosis and treatment of this case. (A) The chest contrast-enhanced CT scan at the first visit to the hospital on July 1, 2021. (B) The 18-FDG PET/CT examination on July 6, 2021. (C) The chest CT scan after 21 days (August 13, 2021) savolitinib neoadjuvant therapy. (D) Postoperative chest x-ray on October 13, 2021 revealed good lung expansion of left lung. (E-G) The patients underwent re-examination of chest CT on December 20, 2021, March 2, 2022, and June 3, 2022 respectively, which showed postoperative changes and no signs of recurrence.
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case_images: The timeline for diagnosis and therapeutic interventions for the patient can be seen in  Figure 4 .