HER2 and EGFR expression in cutaneous spindle squamous cell carcinoma.

BACKGROUND

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.

MATERIALS AND 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.

RESULTS

All 13 cases (100%) evaluated for the presence of HER2 were nonimmunoreactive for the receptor. Only one of the 13 cases (<8%) stained positive for EGFR.

CONCLUSIONS

In several malignancies, the overexpression EGFR and HER2 is associated with clinically aggressive behavior. Despite a limited sample size, EGFR and HER2 are not overexpressed in SSC; this is cognate with the current opinion that SSC possesses limited metastatic potential. With prior reports demonstrating that approximately 80% of cutaneous SCC express EGFR, the negative expression of EGFR and HER2 in SSC presents the potential variable nature of the histologic subtypes of SCC, which can have prognostic and therapeutic implications.