混合型小細胞肺癌の治療経験

Study of Combined Small Cell Lung Cancer

混合型小細胞肺癌は，小細胞肺癌の唯一の亜型である．混合型小細胞肺癌は非小細胞肺癌の成分を伴った小細胞肺癌であり，非小細胞肺癌の成分の中には大細胞神経内分泌癌も含まれる1）．小細胞肺癌全体の2〜10％が混合型小細胞肺癌とされ，比較的まれな組織型である2）．しかし，現在までのところその病理組織学的，分子生物学的特徴は十分にわかっていない．

Objective：Combined small cell lung cancer is the only subtype of small cell lung cancer and is a relatively rare histology. However, its histopathological and molecular biological characteristics are not well understood to date.

Methods：There were 512 surgical resections for lung cancer performed in our department from June 1, 2019 to June 1, 2023. Among them, 5 cases （1.0％） were diagnosed postoperatively as combined small cell lung cancer.

Results：The median age was 75 years. Tumor markers showed elevated newron specific enolage （NSE） in all cases measured. Imagingly, all patients had irregular, solid mass shadows on chest computed tomography （CT） scan. Abnormal fluorodeoxyglucose-positron emission tomography （FDG-PET） accumulation was also observed. Postoperative histopathological examination revealed that one patient was staged upstaging from the preoperative stage, and four patients were treated with carboplatin and etoposide as adjuvant therapy.

Conclusions：Preoperative diagnosis of combined small cell lung cancer is difficult, but it is important to keep this disease in mind in terms of preoperative lymph node evaluation. Postoperative adjuvant therapy should be administered as in small cell carcinoma. However, further case series are needed, as gene mutations and treatment with immune checkpoint inhibitors are also attracting attention.