Benzoyl peroxide promotes the formation of melanotic tumors in the skin of 7,12-dimethylbenz[a]anthracene-initiated Syrian golden hamsters.

A two-stage carcinogenesis experiment was performed in Syrian golden hamsters using a single intragastric initiation with 10 mg/kg body weight of 7,12-dimethylbenz[a]anthracene (DMBA) and repetitive topical promotion on the back skin with two different doses (80 and 160 mg, respectively) of benzoyl peroxide in 1 ml acetone. Benzoyl peroxide was administered three times per week over a period of 16 months. The treatment with benzoyl peroxide alone leads to both a generalized hyperpigmentation and skin scaling without formation of any tumors. DMBA initiation alone induces a moderate number of melanotic foci and a small number of palpable melanotic tumors. Both lesions are located in the dermis. Papillomas develop in the epithelia of the tongue, esophagus and especially of the forestomach but not, however, on the back skin. The combined treatment with DMBA and both doses of benzoyl peroxide drastically increases the incidence of dermal melanotic foci and at late stages also that of melanotic tumors. Therefore, in addition to its known ability to promote papilloma and carcinoma formation in the back skin of mice, benzoyl peroxide is also able to promote the formation of melanotic tumors in the dermis of hamsters.