MMP28 and pachyonychia congenita: Histological type (HR = 0.640, P = .031), tumor location (HR = 0.603, P = .015), and radiation therapy (HR = 0.338, P = .009) were statistically significant with HR < 1, whereas histologic grade (HR = 1.544, P = .033) and the expression value of MMP28 (HR = 1.308, P = .018) were independent risk factors in patients with PC.