To elucidate the mechanism for the relapse despite alectinib administration, RNA sequencing analysis was performed for each of the small‐sized tumour cells purified as CD30 negative population at onset, large‐sized tumour cells purified as CD30 positive population at onset, small‐sized tumour cells at the first relapse and large‐sized tumour cells of pulmonary tumours at the second relapse. The gene discussed is TNFRSF8; the disease is neoplasm.