EGFR and MYC gene copy number aberrations are more common in squamous cell carcinoma than keratoacanthoma: a FISH study

Epidermal growth factor receptor ( EGFR ) and MYC genomic aberrations have been described in cutaneous squamous cell carcinoma ( SCC ) but have not been widely investigated in keratoacanthoma ( KA ). EGFR and MYC were evaluated by fluorescence in situ hybridization and immunohistochemistry in 8 verrucae, 19 involuting KA (IKA), 23 classic KA ( CKA ), 6 atypical KA (AKA) and 19 SCC . Increased EGFR gene copy number was seen in 9 of 23 CKA and 14 of 19 SCC (p = 0.03). Increased MYC gene copy number was observed in 7 of 23 CKA and 17 of 19 SCC (p = 0.0001). MYC gene amplification was more common in SCC than CKA (p = 0.005), while EGFR gene amplification was rare and not significant. MYC protein overexpression was identified in 6 of 23 CKA and 14 of 19 SCC (p = 0.005). There was no statistical difference in EGFR protein overexpression in SCC and CKA (p = 0.06). EGFR and MYC aberrations were rare in IKA. AKA showed EGFR and MYC anomalies at an incidence intermediate between CKA and SCC . EGFR and MYC gene copy number aberrations are more common in SCC than KA . The incidence of aberrations parallels the degree of cytologic atypia in KA .