[Histochemical phenoloxidase demonstration in tumors of the melanocytic system].

Investigations of tissues from a naevus pigmentosus and 5 malignant melanomas were carried out. In malignant melanomas, the number of phenoloxidase reactive cells and the quantity of preformed pigment are very variable. It is discussed whether the in vitro phenoloxidase reactive cells and the in vivo pigment formation can be interpreted as expression of a cell mediated immunological defence reaction.