The development of FAPI as a theranostic tool would theoretically enable the ‘search-and-destroy’ of these metastasis-initiating cells: 131I-labelled or 90Y-labelled FAPI could not only target the FAP-positive tumour bulk (through its endothelium and stroma), but possibly also disseminated FAP-positive metastasis-initiating tumour cell populations. The gene discussed is FAP; the disease is neoplasm.