INTRADERMAL TRANSPLANTATION OF HEPATOMA-CELLS IN GUINEA-PIGS - A MODEL OF EARLY CANCER

Small numbers of hepatoma cells were transplanted intradermally in the flanks of strain-2 guinea pigs to study the course of growth when the size of the transplant was comparable to an early stage of spontaneou s cancer. The incidence of positive transplants and the time for the a ppearance of the tumor were related to the number of cells transplante d. When 40,000 or 80,000 cells were transplanted, tumor developed at 9 8-100% of the sites, but only 60% of the sites that received 5,000 cel ls developed tumors. When 40,000 or 80,000 cells were injected, a meas urable tumor appeared within 10 to 12 days, whereas when 20,000 cells were injected, 20 days were required. The size of the tumor was determ ined by measuring the average diameter, (length + width)/2, of the tum or. The growth rate of the developed tumor is independent of the numbe r of cells transplanted. The initial growth rate of the tumors was 0.3 2 mm/day. When the diameter of the tumor was between 14 and 20 mm, the growth rate decreased to 0.26 mm/day; and regression began when the t umor diameter reached 20 mm.