Porocarcinoma Concurrent with Psoriasis Vulgaris: The First Report.

Psoriasis is a common chronical inflammatory skin disease with a prevalence of 2%-4% worldwide. In contrast, porocarcinoma is a relatively rare cutaneous neoplasm and an associated localization of both lesions is rare. Here, we describe the first case of porocarcinoma in a patient with psoriasis. A 71-year-old Japanese man was referred to our clinic for evaluation of nodule within a keratotic plaque of 20-years history on his leg. Histopathological examination showed that the plaque revealed acanthosis with regular elongation of rete ridges, agranulosis and the presence of Munro microabscesses. In contrast, massive proliferation of atypical poroid cells and a few cuticular cells in the dermis were seen in the nodule. We speculated that it is likely the porocarcinoma was caused by the elevated risk of skin cancer due to chronic inflammatory process of psoriasis itself in our patient.