History: 0108js He has a plaque on the thigh which has changed recently with the developemnt of small pustules. DD Fungal infection, ? Sweet's syndrome Exclude a skin cancer

Description: Lichenoid reaction

Comments: Sections show a biopsy of skin in which there is marked spongiotic vesiculation of the epidermis. Lymphocytes and some eosinophils are present within the spongiotic vesicles. In addition there is lichenoid change involving the basal epidermis. This is accompanied by a dense band-like infiltrate of lymphocytes and some eosinophils in the upper dermis. These lymphocytes show exocytosis into the epidermis with some obscuring of the dermo-epidermal interface. A few of the lymphocytes extend around mid dermal blood vessels also. No fungal organisms can be seen. The differential diagnosis lies between the spongiotic form of fixed drug eruption and a lymphomatoid allergic contact dermatitis.