Three key genes, VCAN, COL4A1 and COL5A2, may be involved in multiple activated signalling pathways in basal cell carcinoma, and they are co-enriched in extracellular space, extracellular region and endoplasmic reticulum lumen, extracellular matrix (Fig. 2E, F). Here, COL5A2 is linked to basal cell carcinoma.