title: Ultraviolet radiation-induced skin tumors in a South American opossum (Monodelphis domestica).
abstract: A total of 19 male and 21 female South American opossums (Monodelphis domestica) were exposed to 250 J/m2 ultraviolet radiation from FS-40 sunlamps (280-400 nm) three times weekly for 70 weeks. The backs of the opossums were shaved as necessary to remove hair. In order to prevent photoreactivation of ultraviolet radiation-induced pyrimidine dimers by the light-dependent photolyase enzyme of the opossum, ultraviolet radiation-exposed opossums were housed under red lights (600-800 nm). The opossum photolyase requires light in the 320-450 nm range for its activity. Twenty-nine control opossums (14 males and 15 females) were irradiated by fluorescent lights with emission spectra primarily in the visible light range (320-700 nm); these control opossums were also housed under red lights, and their backs were also shaved to remove hair. No skin tumors were observed in control opossums, while ultraviolet radiation-exposed opossums developed a variety of hyperplastic and neoplastic skin lesions on the backs and on a single ear. Hyperplastic lesions included foci of epithelial hyperplasia, dermal fibroplasia, and focal proliferation of dermal melanocytes. A total of 20 ultraviolet radiation-exposed opossums (50%) developed skin tumors, and 13 opossums (32.5%) had more than a single tumor. Epithelial tumors included 25 papillomas, four keratoacanthomas, seven carcinomas in situ, three microinvasive squamous cell carcinomas, two invasive squamous cell carcinomas, and a single basal cell tumor. Ten dermal spindle cell tumors also occurred; most of these appeared to be fibrosarcomas. Two benign melanomas and one malignant melanoma were observed.
authors.affiliation: Lovelace Medical Foundation, Biomedical Research Division, Albuquerque, NM.
authors.forename: D F
authors.initials: DF
authors.lastname: Kusewitt
authors.forename: L A
authors.initials: LA
authors.lastname: Applegate
authors.forename: R D
authors.initials: RD
authors.lastname: Ley
mesh_terms: D000818:Animals; D002278:Carcinoma in Situ / Q000473:pathology / Q000662:veterinary; D002280:Basal Cell Carcinoma / Q000473:pathology / Q000662:veterinary; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000662:veterinary; D005260:Female; D006965:Hyperplasia; D007636:Keratoacanthoma / Q000473:pathology / Q000662:veterinary; D008027:Light; D008136:Longevity; D008297:Male; D008545:Melanoma / Q000473:pathology / Q000662:veterinary; D009381:Neoplasms, Radiation-Induced / Q000473:pathology / Q000662:veterinary*; D009893:Opossums; D010212:Papilloma / Q000473:pathology / Q000662:veterinary; D012867:Skin / Q000473:pathology / Q000528:radiation effects; D012878:Skin Neoplasms / Q000473:pathology / Q000662:veterinary*; D014466:Ultraviolet Rays / Q000009:adverse effects*