Epidermal growth factor receptor expression is predictive of poor prognosis in feline cutaneous squamous cell carcinoma

The aim of this study was to investigate epidermal growth factor receptor (EGFR) expression in feline cutaneous squamous cell carcinoma (FC-SCC) and assess its prognostic role. Nineteen formalin-fixed paraffin-embedded excisional biopsies of FC-SCC were tested for EGFR expression using immunohistochemistry (IHC). Relationships between EGFR expression and histopathological parameters (differentiation, mitotic activity), disease-free interval (DFI) and overall survival (OS) at 24 months were further investigated. Fourteen of 19 tumours (73.7%) were positive for EGFR, with great variation in intensity and proportion of labelled cells. EGFR expression was not correlated with tumour differentiation or mitotic activity. Nine cats (47.4%) died of tumour-related causes. Patients with EGFR-positive tumours had a significantly worse outcome (P = 0.0217), with decreased DFIs (P = 0.0075) and survival times (P = 0.0391). These data suggest that EGFR expression carries a negative prognostic significance in FC-SCC. EGFR inhibitors in association with conventional treatments may improve outcome for the subgroup of cats with EGFR-positive tumours.