Figure 1.

Clinical and histopathological phenotype of progressive epidermal nevi in a Chihuahua mix. (a,b) Clinical phenotype at 7 months of age. Pronounced lateralization of the skin lesions at the initial presentation on the right axillary area (a) and right side of ventral/inguinal area (b). (c,d) Clinical phenotype at 27 months of age. Progression of the severity and extent of epidermal nevi to involve diffuse areas in the axillae, ventral abdomen, and inguinal region (c) as well as head, both inner ear pinnae, neck, and dorsal and lateral trunk (d). (e) Histopathology of a skin biopsy taken at 27 months of age from the ventral neck showing severe parakeratotic hyperkeratosis and acanthosis with broad rete ridges extending deep into the superficial dermis. Follicular infundibula are similarly affected by acanthosis and hyperkeratosis and appear distended. (f) Details of the histopathology at higher magnification.