Dermoscopic features of infundibular keratinising acanthomas and follicular cysts: Description, assessment and histopathological correlation

Background: Dermoscopy is a noninvasive technique used for the preliminary assessment of skin lesions including neoplasms in humans and animals. Infundibular keratinising acanthoma (IKA) is a benign hair follicle neoplasm of dogs reported to represent 3.36% of all skin tumours; however, its dermoscopic features have not been investigated. Hypothesis/Objectives: The aim of this study was to describe and characterise the dermoscopic features of IKA and follicular cysts, highlighting their differential aspects and assessing the interobserver agreement of the dermoscopic parameters. Animals: Thirty-five lesions from 10 client-owned dogs, histologically diagnosed as IKA or follicular cysts, were included in this study. Materials and Methods: The dermoscopic images of the lesions at ×10 magnification were independently evaluated on a computer screen by two ECVD board-certified veterinary specialists and one ECVD resident. Results: Twenty-six IKAs and nine follicular cysts were included. White structureless areas were frequently observed in IKAs (92%) and in follicular cysts (66%). Surface keratin (76%), blood spots (38%) and four-dot clods (7%) were exclusively observed in IKAs, while white lines were detected in 11% of IKAs and 22% of cysts. Blood vessels were observed in 15 of the 26 IKAs and in one of the nine cysts only. Near-perfect interobserver agreement for surface keratin (κ = 0.84) and good agreement for white lines (κ = 0.78), four-dot clods (κ = 0.65), linear irregular vessels (κ = 0.66) and blood spots (κ = 0.64) was found. Conclusions and Clinical Relevance: Dermoscopy represents a useful technique to assess IKA and follicular cysts in dogs.