Malignant melanoma has been induced in the Weiser-Maple guinea pig by prolonged application of 7,12-dimethylbenz(a)anthracene. The tumor shows a biphasic growth pattern analogous to the radial and vertical growth phase of human cutaneous malignant melanoma. It evolves through a predictable series of cellular events classified as intraepidermal melanocytic hyperplasia, dermal melanocytosis, dermal melanocytoma, malignant melanoma without intralesional transformation, and, finally, malignant melanoma with intralesional transformation, which is characterized by the appearance of “new kinds of cells” and is associated with widespread metastases and massive lymph node involvement. Clinically, the lesions evolve from diffuse hyperpigmentation to brown-black macules, to nodules of increasing size, to overt malignant melanoma associated with metastases, wasting, and death. Examples of intralesional transformation analogous to that in guinea pigs are found not only in human malignant melanomas, but in other human neoplastic systems, and such analogous cellular events are discussed in this paper.

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This work was supported by Grants NO1-CP-33200, CA-11511, and CA-12923 from the National Cancer Institute. This is the first in a series of reports that will delineate the developmental biology of guinea pig cutaneous malignant melanoma.

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©1976 American Association for Cancer Research.
1976
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