Morbus Bowen cases more often express p16 than cases of invasive squamous cell carcinoma of the skin. Pathobiology of Morbus Bowen includes parallel expression of p53 and p16 or pRb. p53 Expression in Morbus Bowen correlates with HPV genotype in tumor cells. Pathogenesis of invasive squamous cell carcinoma of the skin includes different set of events than pathogenesis of Morbus Bowen.