4 Dermatopathology Epidermolytic hyperkeratosis • Coarse, irregular hypergranulosis associated with disruption of cell membranes • Associated with keratin 1 and 10 mutations Epidermotropism • Lymphocytes in epidermis with relative absence of spongiosis: term usually reserved for mycosis fungoides Erosion • Loss of the epidermis Exocytosis • Lymphocytes in the epidermis with associated spongiosis: term usually used when discussing spongiotic dermatitis Festooning • Papillary dermis retains an undulating pattern (often used to describe porphyria cutanea tarda) Flame figure • Collagen encrusted with major basic protein from eosinophils Figure 1-12 Epidermolytic hyperkeratosis Figure 1-13 Epidermotropism, mycosis fungoides Figure 1-14 Lymphocyte exocytosis, subacute spongiotic dermatitis a b Figure 1-15 Flame figure, Well’s syndrome