ABSTRACT
The formation of melanoma appears to parallel the progression of tumorigenesis. The melanomas in Xiphophorus fish have their origin in polymorphic pigment cell patterns. Several species exhibit these patterns, which represent spots or stripes on the fins or flank; the patterns are composed of distinct, large, melanin-bearing pigment cells called macro-melanophores. The occurrence of a melanoma depends on the genetic composition of both the complex macromelanophore factor and the foreign gene pool into which it is introduced. When using different laboratory swordtail strains, the severity of the melanoma in the backcross hybrids is strain specific. In principle, reciprocal crosses also yield melanoma in backcross hybrids. The maternal effect of increasing melanoma severity may be directly or indirectly connected to those factors governing the early migration in both the platyfish and the melanoma hybrids. One can imagine that the early migrating cells in a swordtail background do not encounter the proper microenvironment during migration or at their final destination.
