TNFRSF8 and lymphoma: In this proof-of-concept study, we evaluate the use of mass cytometry (CyTOF) as an analytical tool to study the uptake of non-radioactive radiopharmaceutical surrogates at the single-cell level.<h4>Results</h4>The preclinical immunoconjugate DOTA-cAC10, targeting CD30 (a receptor overexpressed in lymphomas), was labeled either with radioactive lutetium-177 (<sup>177</sup>Lu) resulting in the [<sup>177</sup>Lu]Lu-DOTA-cAC10 radioimmunoconjugate, or stable lutetium-175 (<sup>175</sup>Lu), yielding the surrogate [<sup>175</sup>Lu]Lu-DOTA-cAC10.