[Role of electron microscopy in determining the degree of differentiation and cell type in oat cell carcinoma of the lung].

Ultrastructurally, small cell carcinoma of lung may be classified as follows: Type I -- undifferentiated small cell carcinoma in which cells do not show any ultrastructural signs of organ- or tissue-specific differentiation. Type II -- differentiated small cell carcinoma consisting of two groups of cells: undifferentiated (without ultrastructural organ-or tissue-specific features) and differentiated (with ultrastructural organ-or tissue-specific features). Type II may occur in different modifications depending on the variety of differentiated cells, e. g. endocrine, mucous, alveolocytic, squamous-cell, mixed, etc. Histologically, small cell carcinoma of lung is represented by a heterogenous group of tumors. Application of electron microscopy provides an objective and reliable means of identification of type and stage of differentiation of cells of this carcinoma.