Currently, many differentially expressed genes related to signal transduction are known to play roles in the development of PC that include the stimulation of protooncogenes, such as K-ras [100, 101], HER-2/neu [102, 103], and BRCA [104, 105], and the inactivation of tumor suppressor genes, such as SMAD4 [106], APC [107], P53 [108, 109], and CDKN2A [110, 111]. The gene discussed is ERBB2; the disease is pachyonychia congenita.