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The Use of Electron Microscopy and Im- munohistochemistry in the Diagnosis and Understanding of Lung Neoplasms. Hammar, S. Department of Pathology, The Mason Clinic, Seattle, WA 98111; U.S.A. Clin. Lab. Med. 7: 1-30, 1987.

This article has presented informa- tion concerning the ultrastructural features and, to a lesser degree, the immunohistochemical characteristics of lung neoplasms. Electron microscopy and immunohistochemistry are useful tech- niques for diagnosing and understanding common and rare lung tumors. Electron microscopy is particularly helpful in accurately diagnosing undifferentiated lung tumors such as large-cell undif- ferentiated and small-cell undifferen- tiated carcinomas. Ultrastructural studies of lung tumors have also aided in overall understanding of the his- togenesis of these tumors. Electron microscopy and immunohistochemistry are techniques that can be applied to tiny specimens, including those obtained via fine-needle aspiration biopsy, and to cells obtained from pleural fluid. An intelligent use of electron microscopy and immunohistochemistry aids in the diagnosis and understanding of lung neoplasms.

Heterogeneity of Lung Cancer: The Problem of Sample Error in Diagnostic Electron Microscopy. Mooi, W.J., Dingemans, K.P., Wagenaar, S.Sc. et al. Department of Pathology, Academic Medical Centre, Amsterdam, The Netherlands. Eur. J. Respir. Dis. 149: 45-52, 1987.

We studied the ultrastructure of superficial and deep samples of 40 resected primary lung carcinomas. Tumour cell differentiation was semi- quantitatively assessed and differences between samples of a same tumour were evaluated. In two instances were major differences in ultrastructural diag- nosis found between the samples of the same tumour. A further 9 cases showed one predominant differentiation in one sample, but two equally predominant differentiations in the second sample. The other 29 tumours did show oc- casional minor differences between the samples, but these differences did not result in differences in ultrastruc- tural diagnosis.

The Distinction of Adenocarcinoma from Malignant Mesothelioma in Cell Blocks of Effusions: The Role of Routine Mucin Histochemistry and Immunohistochemical Assessment of Carcinoembryonic Antigen, Keratin Proteins, Epithelial Membrane Antigen, and Milk Fat Globule-Derived Antigen. Cibas, E.S., Corson, J.M., Pinkus, G.S. Department of Pathology, Brigham and

Women's Hospital, Boston, MA 02115, U.S.A. Hum. Pathol. 18: 67-74, 1987.

The immunohistochemical profile (i.e., carcinoembryonic antigen, karatin proteins, epithelial membrane antigen, human milk fat globule-derived antigen, and mucin) of paraffin- embedded cell blocks of 20 malignant effusions from patients with malignant mesothelioma was compared with that of 39 malignant effusions from patients with metastatic adenocarcinomas to determine whether these markers distin- guished between these tumor types. Twenty-three adenocarcinomas (59 per cent) stained for mucin. Immunoreac- tivity for carcinoembryonic antigen (CEA) was observed in 28 adenocar- cinomas (72 per cent). All were im- munoreactive for keratin proteins, and 29 adenocarcinomas (74 per cent), in- cluding seven that were mucin and CEA negative and exhibited a 'peripheral predominant' staining pattern for keratin proteins. By contrast, none of the mesotheliomas stained for mucin or for CEA, and, although all were im- munoreactive for keratin proteins, none demonstrated a peripheral predominant pattern of staining. Epithelial membrane antigen and milk fat globule- derived antigen were identified in the majority of both mesotheliomas and adenocarcinomas. Neither staining in- tensity nor pattern of reactivity of these markers clearly distinguished the tumors. This study of cell blocks of serous effusions suggests that staining for mucin, immunoreactivity for car- cinoembryonic antigen, and a peripheral predominant pattern of reactivity for keratin proteins represent highly characteristic markers of adenocarcinomas, which identify the majority of these tumors (38 or 39) and allow their distinction from malignant mesotheliomas.

Intercellular Junctions and Tumor Stage in Small Cell Carcinoma of the Lung. Vollmer, R.T., Shelburne, J.D., Iglehart, J.D. Department of Pathology, Duke University Medical Center, Durham, NC, U.S.A. Hum. Pathol. 18: 22-27, 1987.

The authors have studied the ultrastructural features of 52 cases of oat cell carcinoma of the lung and have related their observations to tumor stage and patient survival. Only the type of cell junctions seems to be of prognostic importance. Tumors with in- termediate junctions - and especially those with desmosomes - have a more lo- calized stage and may be resectable to result in longer survival than expected for oat cell carcinomas without junctions. For example, in the authors' series the median survival periods for those with no identifiable junctions,