A combined small cell lung carcinoma patient with only small cell carcinoma components in mediastinal lymph node metastasis and chondrosarcoma-like components in liver metastasis.

A 69-year-old ex-smoker Japanese man presented with a left mediastinal lymph node and left upper lobe tumour. Bronchoscopic biopsy specimens from the enlarged left mediastinal lymph node and left upper lobe tumour revealed small cell lung carcinoma (SCLC). He was treated with first-line chemotherapy with carboplatin, etoposide, and atezolizumab for four courses and subsequent atezolizumab maintenance therapy. However, his left upper lobe lung tumour only increased in size, and left upper lobectomy revealed combined SCLC (adenocarcinoma and chondrosarcoma-like features). Four months after lobectomy, liver metastasis of chondrosarcoma-like features (similar to pathological findings of the left upper lobe tumour) were observed. Combined SCLC, including sarcomatous components, is rare and poorly responds to chemotherapy. The metastases of combined SCLC in this patient were of only one type of histological component, making diagnosis and treatment difficult. If treatment for SCLC responds inadequately, considering combined SCLC and actively re-examining histological diagnosis is necessary.