HER2 and EGFR Expression in Cutaneous Spindle Squamous Cell Carcinoma

Epidermal growth factor receptor (EGFR) and HER2, members of the Erb family of transmembrane receptor tyrosine kinases (RTK), are responsible for communicating extracellular signals to the nucleus. Moreover, EGFR and HER2 are implicated in tumorgenesis. Immunohistochemical studies have demonstrated that approximately 80% of cutaneous squamous cell carcinomas (SCC) express EGFR. To date, the expression of EGFR and HER2 has not been evaluated in primary cutaneous spindle squamous cell carcinoma (SSC). In extracutaneous spindle squamous cell carcinoma, there is evidence implicating the expression of RTK as a strong, independent prognostic indicator of potentially poor outcome. The purpose of this study is to investigate the expression of EGFR and HER2 in SSC, using immunohistochemical methods. Thirteen cases of primary nonmetastatic cutaneous SSC archived at a large veterans' hospital and tertiary referral dermatopathology service were retrieved via a computer-assisted search. Immunohistochemistry was used to evaluate the presence of EGFR and/or HER2 expression. All cases were confirmed before study by a single, board-certified dermatopathologist. All 13 cases (100%) evaluated for the presence of HER2 were nonimmunoreactive for the receptor. Only one of the 13 cases (