본 증례는 epidermal growth factor receptor 돌연변이 비소세포폐암 환자에서 lazertinib 치료 중 췌장 전이 병변에서 소세포암 전환이 발생한 드문 사례를 보고하였다. 소세포암 전환은 치료 저항성의 기전을 나타내며 이를 확인하기 위해 조직 생검이 중요하다. Tyrosine kinase inhibitor 치료 중 병변의 선택적 진행이 의심될 때는 조직학적 평가를 통해 전환 여부를 확인하고 이에 따른 치료 전략을 변경할 필요가 있다.

Lazertinib is an oral, third-generation, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) for the treatment of non-small cell lung cancer (NSCLC). This case report presents a rare instance of small cell carcinoma transformation in pancreatic metastasis in a patient with EGFR-mutated NSCLC undergoing treatment with lazertinib. Small cell carcinoma transformation indicates a mechanism of treatment resistance, and tissue biopsy is essential to confirm this. When isolated progression of a lesion is suspected during TKI therapy in EGFR-mutated NSCLC, histological evaluation is necessary to confirm the transformation for the treatment strategy.

• 김재환(서울대학교 의과대학 분당서울대학교병원 내과) | Jaihwan Kim (Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea) Corresponding author
• 황진혁(서울대학교 의과대학 분당서울대학교병원 내과) | Jin-Hyeok Hwang (Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea)
• 이종찬(서울대학교 의과대학 분당서울대학교병원 내과) | Jong-Chan Lee (Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea)
• 정광록(서울대학교 의과대학 분당서울대학교병원 내과) | Kwangrok Jung (Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea)
• 임희언(서울대학교 의과대학 분당서울대학교병원 내과) | Hee-Eon Lim (Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea)
• 김현기(서울대학교 의과대학 분당서울대학교병원 내과) | Hyeon-Gi Kim (Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea)
• 서우택(서울대학교 의과대학 분당서울대학교병원 내과) | Wootaek Seo (Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea)