Chromosomes of human cancer cells.

Obvious mitotic abnormalities have long been known to occur very commonly in malignant tumours, but as a result of recent improvements in technique much more reliable cytogenetic observations are now possible. Transplantable tumours were the first to be accurately examined, and these were found to consist of populations of cells with variations around a modal (" stemline ") type which differs in each tumour (Makino and Kano, 1953; Hauschka, 1953). Before 1956 cytological technique did not permit very exact analysis of human material, and until that date the normal human chromosome number of 46 was not known; however, several investigators performed counts and analyses of human malignant cells (Koller, 1947, 1956; Timonen, 1950; Hsu, 1954; Fritz-Niggli, 1955, 1956; Manna, 1955; Hansen-Melander, Kullander, and Melander, 1956; Levan, 1956; Ising and Levan, 1957). Since the introduction of hypotonic pretreatment it has been confirmed that abnormal stemline karyotypes are regularly present in naturally occurring malignant tumours, both of animals (Ford, Hamerton, and Mole, 1958) and of man (Wakabayashi and Ishihara, 1958; Tabata, 1959; Makino, Ishihara, and Tonomura, 1959; Ishihara, 1959; Tonomura, 1959a, 1959b, 1960; Ishihara, Moore, and Sandberg, 1961). During the past two years we have been collecting material from cases of human malignant disease, and making preparations to demonstrate the chromosomes. In this paper only the main results are summarized to