34

cancers. Quantitatively, mesotheliomas con- taine~ statistically greater amounts (mean value, 0.74 mg/g) of HA than primary lung adenocarcinomas (mean value, 0.08 mg/g), but were not statistically different from soft tissue sarcomas (mean value, 2.01 mg/g) or primary ovarian serous neoplasms (mean value, 0.92 mg/g). The study concludes that, contrary to previous reports, HA is neither the sole nor the predominant glycosaminogly- can in most mesotheliomas, but, given the proper clinical and histologic setting, the finding of sufficiently high levels (greater than 0.4 mg/g dry tissue extract) supports the diagnosis of mesothelioma when the alternative diagnosis is primary adenocar- cinoma of the lung.

Localized Fibrous Mesothelioma: An Immuno- histochemical and electron Microscopic Study. Said, J.W., Nash, G., Banks~Schlegel, S., et.al. Division of Anatomic Pathology, Ce- dars-Sinai Medical Center, Los Angeles, CA 90048, U.S.A. Hum.Pathol. 15: 440-443, 1984.

The absence of keratin staining in tumor cells from localized fibrous mesotheliomas in both paraffin-embedded and frozen sections with sensitive peroxidase-antiperoxidase and avidin-biotin techniques is described. In addition to the absence of staining for whole-stratum cor~eum keratin proteins, sections were negative for keratins of dif- ferent molecular weights (45, 55, and 63 kilodaltons) that are characteristically present in mesothelial cells. Ultrastructu- rally, the cells most closely resembled me- senchymal cells of the fibroblastic type. These findings are in accordance with recent theories that relate the derivation of loca- lized fibrous mesotheliomas to nonmesothe- lial cells, including subpleural connective tissue. Based on differences in immunohisto- chemical staining, the tumors appear to be unrelated to diffuse malignant mesothelio- mas.

Histologic Type of Lung Cancer and Asbestos Exposure. Auerbach, 0., Garfinkel, L., Parks, V.R., et al. Veterans Administration Medical Center, East Orange, NJ 07019, U.S.A. Cancer 54: 3017-3021, 1984.

The histologic types of lung cancer in 855 patients (848 men and 107 women) from three hospitals and one international study of insulation workers were evaluated. Of these, 196 cases had asbestos exposure. About one half of the cases were diagnosed from surgical slides and one half from autopsy slides. Squamous cell carcinoma constituted the largest percentage of tumor types and was found with the same frequency in exposed and nonexposed groups. Small cell carcino-

ma was found in 25% of the exposed and in 15% of the nonexposed patients. Upper lung sites were involved in about two thirds of the cases with asbestos exposure and lower lobes in the other one third. There was little difference in histologic type in cases regardless of whether upper or lower lobes were involved. Cigarette smokers who smoked until their cancer diagnosis showed no difference in histologic type by amount smoked, and slight but not statistically significant differences from ex-cigarette smo- kers.

}~istological Types of Malignant Mesothelioma and Asbestos Exposure. Wright, W.E., Sherwin, R.P. Department of Pre- ventive Medicine, University of Southern Cali- fornia School of Medicine, Los Angeles, CA 90033, U.S.A. Br. J. Ind. Med. 41: 514-517, 1984.

The Los Angeles County Cancer Surveillance Program abstracts hospital pathology records on almost all cases of cancer occurring in the county. Those cases of pleural and peritoneal mesothelioma that occurred between 1972 and 1978 were identified. Occupational histories were obtained from interviews, and the histo- pathology of the tumours was reviewed by a mem- ber of a mesothelioma reference panel who was unaware of the exposure histories. The relation of asbestos exposure to the three histological types of mesothelioma (epithelial, mesenchymal, and mixed) was studied among the 29 cases for whom occupational histories were available and who were also considered to have histopathology consistent with mesothelioma. The proportion of cases exposed to asbestos was high for both the epithelial (11/17, 65%) and mixed histological types (6/11, 55%). The single case of mesothe- lioma classified as a mesenchymal type was also exposed to asbestos. Cases who had worked in shipyeards were represented in each of the three groups. In cases who had worked in asbe- stos production and manufacture an exclusively epithelial type of tumour was observed. In cases who had worked as insulators or in heating trades the histological type was predominantly (3/4) mixed. These data do not support the hypo- thesis that any specific histological type of mesothelioma is especially related to asbestos exposure.

The Prognostic Significance of Histologic Sub- typing in Small Cell Carcinoma of the Lung. Choi, H., Rameniuk, E., Byhardt, R.W., et al. Department of Pathology, Medical College of Wisconsin, Milwaukee, WI 53193, U.S.A. Am. J. Clin. Oncol., Cancer Clin. Trials 7: 389-397, 1984.

Previously untreated patients with small cell carcinoma of the lung (SCCL), who were treated at the Medical College of Wisconsin with combined chemotherapy and radiation thera- py, were retrospectively subtyped according to the 1981 World Health Organization Lung Cancer