Heterogeneity of lung cancer: the problem of sample error in diagnostic electron microscopy.

We studied the ultrastructure of superficial and deep samples of 40 resected primary lung carcinomas. Tumour cell differentiation was semiquantitatively assessed and differences between samples of a same tumour were evaluated. In two instances were major differences in ultrastructural diagnosis 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 occasional minor differences between the samples, but these differences did not result in differences in ultrastructural diagnosis.