Ultrastructural features of large cell carcinoma of the lung with reference to the prognosis of patients.

Epon embedded sections of large cell carcinoma of the lung obtained from 26 patients were examined by light and electron microscopy. On an ultrastructural basis this carcinoma was subclassified into four types: squamous, adenosquamous, adenocarcinomatous, and giant cell types. The giant cell carcinoma was regarded as a special type of squamous or undifferentiated carcinoma. Transition between each of these types was clearly demonstrated. Follow-up study revealed that a close correlation existed between these types and the prognosis of the patients, the squamous type showing a better prognosis and the adenosquamous and adenocarcinomatous types exhibiting equally poor prognoses. The giant cell type invariably pursued a fulminant course. It was suggested that each of the types might represent different stages and directions of differentiation of cancer cells originating from the same ancestry. The authors' view favors the Y construct theory concerning the histogenetic pedigree of pulmonary carcinoma.