The utility of fine-needle aspiration cytology in the differential diagnosis of cutaneous masses containing keratin

Fine needle aspiration (FNA) cytology is commonly used to evaluate canine cutaneous and subcutaneous masses in a clinical setting. Neoplastic and non neoplastic canine cutaneous masses containing keratin (CMCK) are a common finding in dogs; however a specific presurgical diagnosis by cytology is useful for the correct surgical approach. Few studies have addressed the accuracy of FNA cytology in the evaluation of CMCK. The purpose of this study was to describe cytological features and compare the cytology and histopathology of CMCK in dogs. Specimens of 23 CMCK from 21dogs were retrospectively evaluated. Cytological specimens were obtained by FNA prior to surgery. Post-surgical tissue specimens were routinely processed for histopathology. A cytological diagnosis of neoplasia was achieved in six cases confirmed by histology (all true positive). Negative cytology for neoplasia was obtained in 17 cases (10 true negative, 7 false negative). Cytology had an overall 69,6% agreement with histopathology, with a specificity of 100%,a sensitivity of 46%, a predictive value of positive test of 100% and a predictive value for negative test of 58,8%. According with these results, cytology is a good diagnostic tool for neoplastic CMCK and should be utilized to assist in the definition of the best surgical approach to CMCK