Malignant fibrous histiocytomas induced by 4-(hydroxyamino)quinoline 1-oxide in rats.

Subcutaneous and bone malignant fibrous histiocytomas (MFH) were induced in high incidence in rats by 4-(hydroxyamino)-quinoline 1-oxide (4-HAQO). Subcutaneous MFH were induced locally by repeated weekly injections of 1 mg 4-HAQO/rat for 4 weeks. Between 16 and 48 weeks after the final treatment, 13/15 (87%) male noninbred Wistar rats developed tumors. The histologic subtypes of these tumors were as follows: 11 fibrous, 1 myxoid, and 1 giant cell. Bone MFH were induced between 18 and 25 weeks by implantation of 4-HAQO (8 mg/rat) into the bone marrow of the tibia in 12/14 (86%) male noninbred Fischer 344 rats. The histologic subtypes of these tumors were as follows: 6 fibrous, 4 myxoid, and 2 giant cell. Morphologically, these MFH appeared similar to human MFH.