Is Ki-67, keratin 16, involucrin, and filaggrin immunostaining sufficient to diagnose inflammatory linear verrucous epidermal nevus? A report of eight cases and a comparison with psoriasis vulgaris*

Inflammatory linear verrucous epidermal nevus and linear psoriasis are sometimes hard to differentiate clinically and pathologically. Although immunohistochemical expression of keratin 10 (K10), K16, Ki-67, and involucrin may be useful for differentiating both entities, these results have been reported in only a few cases. We collected data from 8 patients with inflammatory linear verrucous epidermal nevus, 11 with psoriasis vulgaris, and 8 healthy controls and evaluated immunohistochemical expression of Ki-67, K16, involucrin, and filaggrin among them. Ki-67 and K16 overexpression was similar in inflammatory linear verrucous epidermal nevus and psoriasis vulgaris compared with normal skin. Although staining for involucrin showed discontinuous expression in parakeratotic regions in 4 inflammatory linear verrucous epidermal nevus cases, it was continuous in the other 4 cases and in all psoriasis vulgaris cases. Filaggrin expression was present in hyperkeratotic regions but scarce in parakeratotic areas in both inflammatory linear verrucous epidermal nevus and psoriasis vulgaris. The immunostaining pattern of Ki-67, K16, involucrin, and filaggrin may be insufficient to discriminate inflammatory linear verrucous epidermal nevus from psoriasis vulgaris.