Lung spindle cell carcinoma harbouring a constitutively active epidermal growth factor receptor mutation

Lung spindle cell carcinoma is a rare lung tumour with a poor prognosis, and its standard therapy has not been established. Furthermore, little work has been conducted on the genetic characteristics of lung spindle cell carcinomas. Here, we report an 82‐year‐old woman who was referred to our hospital due to a fever and dyspnoea. Chest computed tomography demonstrated a 75‐mm mass surrounded by infiltrates and atelectasis in the right upper lobe. She was eventually diagnosed with lung spindle cell carcinoma corresponding to clinical stage IVB (cT4N2M1c(ADR)). A genetic study indicated that epidermal growth factor receptor (EGFR) exon 19 was deleted in the tumour cells. She received gefitinib as first‐line therapy. However, no significant effect was observed, and she died of respiratory failure 89 days after the initial admission. To our knowledge, this is the first case of spindle cell carcinoma of the lung in which a sensitizing EGFR mutation is detected.