[Ultrastructural evaluation of pulmonary adenocarcinoma. II. Phenotype heterogeneity and classification]

A phenotypical heterogeneity was observed in 45 tumours (45 per cent) from a group of 102 carcinomas with ultrastructural features of exocrine differentiation. Double heterogeneity was found in 36 tumours and a triple one in 8 tumours; a case with quadruple heterogeneity was presented analogy of which has been lacking in literature. A combination of different exocrine phenotypes occurred in 12 tumours, exocrine and endocrine phenotypes combined in 18 tumours, exocrine cells and keratinocytes were found in 21 tumours. The exocrine phenotype was characterized usually (38 times) by secretion granules mostly of a serous type (19 times), cells with microvillous specialization without granules represented (15 times) a lower level of the exocrine phenotypical differentiation. A ciliary phenotype which could not produce homogenous population of dividing cells yet occurred (4 times) as a rudimentary accompaniment of an endocrine phenotype. The case of quadruple heterogeneity combined ciliary, serous, endocrine and keratinocytic phenotypes. The WHO histological typing scheme does not offer a proper category for heterogenous adenocarcinomas with one prevailing exocrine phenotype when compared with an analogous group of "combined" small cell carcinomas. Histological typing of such heterogenous adenocarcinomas is to be completed at least by an electron microscopical prevailing cytological characteristic in the same way as in phenotypically homogenous carcinomas. Heterogenous tumours without any phenotypical prevalence may form a group of mixed carcinomas which has been represented so far only by the histological types of adenosquamous and mucoepidermoid carcinoma.