Similarly, we observed that Goblet-like Club cells (cluster 4), marked by the expression of Ltf and Bpifb1, transition into a pre-tumour stage (cluster 11), which in addition to expressing high levels of Alk, shows the expression of Ltf, Krt5 and Trp63. We speculate that our pre-tumour stage is similar to the Goblet-Basal intermediate stage found in lung regeneration and that Club cells mimic this state during tumour initiation. Here, ALK is linked to neoplasm.