Skin Tumors Induced in Rats by the Dietary Administration of N,N′-2,7-Fluorenylenebisacetamide

Abstract

Tumors and cysts of sebaceous gland origin and tumors derived from the epidermis were induced in female ACI/N rats that ingested N,N′-2,7-fluorenylenebisacetamide in their diet. A total of 7 epidermal tumors, 107 sebaceous gland tumors, and 67 cysts occurred in 19 rats necropsied over a period of 19 weeks, beginning at the 31st week of treatment. The tumors of epidermal origin were present after the 38th week and included 4 papillomas, 1 keratoacanthoma, 1 epidermoid carcinoma, and 1 thickened area of epidermis similar to a folliculoma of man. These tumors occurred around the lips, face, and ear lobes, with never more than 1 per animal. The sebaceous gland tumors and cysts were nearly always multiple. Eighty percent of them developed on the back of the animal with some tendency toward symmetrical distribution. The tumors were believed to be derived from the generative cells of the sebaceous glands. They were composed of mature, foamy, sebaceous cells and undifferentiated cells in various proportions with marked tendency toward differentiation into squamous cells with keratinization; none metastasized. The cysts developed from the matrix portion of the hair bulb and often contained a column of shadow cells. No tumor of connective tissue origin was found. Nonspecific dermatitis occurred in several control and experimental rats, chiefly in those killed early in the experiment.