SPARC and melanoma: While we could not test the latter in heterogeneous CTC populations (the more complex sorting process resulted in poor RNA quality), we found high expression levels of SPARC, FN1 and TNC in 501mel cells from heterogeneous tumours when compared to cells from homogeneous tumours, and importantly, all three factors have been implicated in lung metastasis of melanoma (Fukunaga‐Kalabis et al., 2010; Tichet et al., 2015).