Incidence of chromatoblastomas in aging goldfish (Carassius auratus).

The incidence of chromatoblastomas in aging goldfish, Carassius auratus, was observed for 2 successive years. Tumors first appeared in fish at 5 years of age, and the tumor frequency increased with increasing age of the fish. The cumulative incidence rate of chromatoblastomas and the mean number of tumors per fish were estimated for each age. The mean number of tumors per fish fitted a straight line with a slope of approximately 3 on a double logarithmic graph against age. Thus tumor incidence seemed proportional to about the third power of age, and tumor appearance seemed dependent on some mutational events.