These transcriptome and clinicopathological results reveal that LAD use at least 80% of NKX2‐1 TSSs and expression of the NKX2‐1/TTF‐1 transcript isoform without exon 1 (NKX2‐1_004 and NKX2‐1_005) defines a distinct subset of LAD characterised by aggressive behaviour in elder patients. Here, TTF1 is linked to leukocyte adhesion deficiency.