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Light-microscopic morphology of cell types cultured during preneoplasia from foreign body-reactive tissues and films.

Summary Cells isolated in vitro from preneoplastic foreign body (FB)-reactive capsule tissue or surfaces of FB segments from mice were studied and found to conform to one of four cell-type categories on the basis of light-microscopic morphology, pattern of in vitro appearance, in vitro topographical relationships, and certain karyotype similarities. Euploid type I (macrophage-like) and II (fibroblast-like) cells predominated in primary cultures and early passages (passages 1 and 2) of cells derived from FB-reactive capsule tissue. The observation of small numbers of type III cells (unidentified cell type with unknown karyotype characteristics) in passages 1 and 2 of cells from FB-reactive capsule origin coincided with the deterioration of euploid type II cell populations and preceded the observation of type IV (endothelial-like) cells. Type IV cells had a pronounced growth advantage over cell types I, II, and III, resulting in cultures composed only of type IV cells after three passages. Cultures derived from cells attached to the surfaces of FB segments also conformed to the criteria established for type IV cells. Of the four cell types identified in this study, type IV cells were determined to have special importance regarding the nature of the progenitor cell in FB tumorigenesis, in that they were aneuploid and eventually produced homologous sarcomas when injected as a suspension into compatible hybrid recipient mice. These findings are consistent with our earlier reported hypothesis implicating certain cells of the microvasculature as the likely progenitor cells from which FB sarcomas are derived.