TNFRSF8 and neoplasm: We monitored his serum‐soluble interleukin‐2 receptor (sIL‐2R) levels, the number of tumour cells in the blood using flow cytometric analysis (small‐sized tumour cells; CD30‐5‐8+, large‐sized tumour cells; CD30+), and the expression levels of NPM‐ALK mRNA transcripts in the tumour cells by droplet digital polymerase chain reaction (ddPCR) over time as markers of treatment efficacy (Figure S1).