High frequency of spontaneous histiocytic sarcomas in BDII/Han rats.

Histopathological findings and anatomical distribution of histiocytic sarcomas found in an uncommonly high frequency (50 of 399 rats) in the BD II/Han inbred strain are reported. The incidence of the tumours in male rats was significantly higher than in females. This was in part attributed to a shorter life expectancy of female rats. Tumours identified were composed of histiocytic cells. Other histological features included Langhans-type giant cells, palisading of histiocytes around necrosis and granuloma-like arrangements of cells. The highest incidence of histiocytic sarcomas was found in the subcutis. Other organs frequently involved were lungs and liver. The histopathological findings in BD II/Han rats are compared with previously reported histiocytic sarcomas in other strains of rat.