[Cytological characteristics of carcinoid tumors of the respiratory and digestive organs].
The paper discusses the results of a study of 22 primary and metastatic carcinoids which occurred in respiratory and digestive tracts with varying degree of differentiation. They formed the basis of the following cytologic criteria for their diagnosis: monomorphism of small cell elements, among which dark and clear ones can be distinguished; small-lumped chromatin pattern in nuclei of clear cells; and teniform and perivascular structures. Diagnosis was verified in all cases by histological and histochemical methods which were complemented by electron microscopy in 3 cases. On the basis of the said characteristics, tumors with endocrine differentiation can be distinguished from other pulmonary and digestive tract neoplasms.