Relevance to Humans of Experimentally Induced Pulmonary Tumors in Rats and Hamsters. In: Dungworth DL, Kimmerle G, Lewkowski J, Mcclellan RO, Stöber W, editors. Inhalation Toxicology. Berlin: Springer Berlin Heidelberg; 1988. pp. 209-32. [DOI: 10.1007/978-3-642-61355-5_13]

Spontaneous Neoplastic Lesions in Control Syrian Hamsters in 6-, 12-, and 24-Month Short-Term and Carcinogenicity Studies

Male and female Syrian hamsters of the strain Han: AURA from the Fraunhofer Institute for Toxicology and Experimental Medicine breeding colony were maintained as control animals for five toxicity/carcinogenicity studies and were examined for the presence of neoplastic disease either when they died or when the study terminated. In total, 250 male animals and 250 female animals in three carcinogenicity studies were analyzed as well as the results of a 6-month study (fifty males and fifty females) and a 12-month study (fifty males and fifty females). In the 24-month studies, in the male animals, twenty-five organs were affected with malignant and benign tumors. In the female animals, twenty-four organs were affected with malignant and benign tumors. The most frequently affected tissue in the three 24-month studies was the adrenal gland where 141 cortical adenomas (56.4%) were noted in 250 male animals and 115 cortical adenomas (46%) noted in 250 female animals. In addition, a high incidence of squamous cell papilloma in the vagina was noted in female hamsters on the 24-month studies. A moderate incidence of squamous cell papilloma of the nonglandular forestomach, benign granulosa cell tumor of the ovary, lymphoma of the hemopoietic system, endometrial stromal polyp, and adenocarcinoma of the uterus and islet cell adenoma of the pancreas were also observed on the 24-month studies.

Risk of human health by particulate matter as a source of air pollution--comparison with tobacco smoking

Increased air pollution, containing carcinogenic particulate matter smaller than 2.5 microm (PM(2.5)), has gained particular attention in recent years as a causative factor in the increased incidence of respiratory diseases, including lung cancer. Extensive carcinogenicity studies conducted recently under Good Laboratory Practice conditions by National Toxicology Program in the USA, Ramazzini Foundation in Italy or Contract Research Organizations on numerous chemical compounds have demonstrated the importance of considering dose levels, times and duration of exposure in the safety evaluation of carcinogenic as well as classical toxic agents. Data on exposure levels to chemical carcinogens that produce tumor development have contributed to the evaluation of human carcinogens from extrapolation of animal data. A popular held misconception is that the risk from smoking is the result of inhaling assorted particulate matter and by products from burning tobacco rather than the very low ng levels of carcinogens present in smoke. Consider the fact that a piece of toasted bread contains ng levels of the carcinogen urethane (ethyl carbamate). Yet, no one has considered toast to be a human carcinogen. Future human carcinogenic risk assessment should emphasize consideration of inhalation exposure to higher levels of benzo (a) pyrene and other possible carcinogens and particulate matter present in polluted air derived from automobile exhaust, pitch and coal tar on paved roads and asbestos, in addition to other environmental contaminant exposure via the food and drinking water.

Spontaneous cystic keratinizing epithelioma in the lung of a Sprague-Dawley rat

A spontaneous cystic keratinizing epithelioma in the lung of a 704-day-old female Hsd:Sprague-Dawley rat is described. The rat had a white subpleural discoloration on 1 diaphragmatic lobe at necropsy. Microscopically, a central keratin mass, surrounded by a multilayered squamous epithelium of varying thickness, was found. In the periphery of the tumor, epithelial nests projected multifocally into the adjacent alveolar spaces. Immunohistochemical labeling of nuclei by PCNA (proliferating cell nuclear antigen) revealed proliferative activity in 1 or 2 peripheral cell layers in most locations. To the best of the authors' knowledge, this is the first report dealing with the morphological and immunohistochemical features of a spontaneous cystic keratinizing epithelioma in a rat.