Conversely, the expression levels of piR‐19 004 and piR‐2878 were notably increased, in contrast to piR‐19 166, which showed a significant decrease, with piR‐19 166 identified as a regulator of the cortactin (CTTN)/matrix metalloproteinases (MMPs) pathway, inhibiting migration and metastasis of PC cellss [46] (Figure 3B). The gene discussed is CTTN; the disease is pachyonychia congenita.