Biological behavior of cloned cells of human malignant fibrous histiocytoma in vivo and in vitro.

A human malignant fibrous histiocytoma cell line was established in vitro. Cells showed a wide variety of morphologies, although the karyotype study showed that the tumor was monoclonal in origin because of the presence of unique marker chromosomes in 100% of the cells examined (50 of 50). Cells were cloned according to their characteristic morphologies and biological behavior in culture. The cloned cells were sparse spindle, packed spindle, epithelioid, and lymphoid. In colonies, sparse spindle cells grew separately from each other without cell to cell contact but produced a cartwheel pattern at confluency. Packed spindle cells grew in a tightly packed fashion and produced a storiform pattern at confluency. Epithelioid cells were spindle shaped as individuals but became epithelioid when in contact with each other and produced many multinucleated giant cells at confluency. Lymphoid cells were spindle shaped as individuals but became spherical at confluency. When tumors were grown in nude mice after transplantation of these cloned cells, the histology was shown to be unrelated to morphology in culture and was epithelioid (histiocytic), as was the original tumor. These results show that (a) a single cell derived from malignant fibrous histiocytoma cells exhibits a wide range of phenotypical expression in vitro, (b) cells have their own morphological and biological characteristics in vitro, which (c) however, are easily influenced by environmental factors and (d) which are unstable and even interchangeable. These characteristics may contribute to the endless variety of cellular forms and growth patterns of malignant fibrous histiocytomas in humans.