[Malignant melanoma--a PO-cell tumor? (author's transl)].

In the connective tissue, diffusely scattered phenoloxidase containing cells (PO-cells) can be found by histochemical methods. The same cells were demonstrated in a recurrent malignant melanoma of the skin and in its lymph node metastases. The theory is proposed that PO-cells are the stem cells of malignant melanoma in contrary to the common view that melanoma derives from the melanocytes of the stratum cyclindricum of the epidermis. The occurrence and distribution of PO-cells in the rat give a good explanation for the appearance of metastasis within different organs and tissues.