Grout et al. examined lung tumors via single-cell RNA sequencing combined with multiple imaging techniques and identified two CAF populations related to T cell marginalization, namely (i) myosin heavy chain 11 (MYH11)+SMA+ CAFs, which are present in early-stage tumors and form around aggregated cancer cells in a single cell layer; and (ii) FAP+SMA+ CAFs, which are present in more advanced tumors and are distributed in sheets in the stroma or in several layers around tumor clusters. The gene discussed is SMN1; the disease is neoplasm.