Diaminobenzidine cytochemistry in unfixed human epidermis: a marker for epidermal differentiation and for mitochondria.

Intubation of unfixed and unfrozen slices of skin in diaminobenzidine allows visualization of a peroxidatic activity in perinuclear envelope of suprabasal keratinocytes undergoing orthokeratotic differentiation. Basal keratinocytes and melanocytes are always negative. This enzyme is absent in mucous and parakeratotic (psoriatic) differentiation. Mitochondria are also strongly stained by this technique and it was shown that the number of epidermal mitochondria is greatly increased in psoriatic lesions.