Exfoliative cytopathology of atypical pulmonary carcinoid: a case report.

A 35-year-old man was diagnosed as having lung cancer and died six years later. In spite of an initial histological diagnosis of squamous cell carcinoma from the biopsy material, the correct diagnosis of atypical carcinoid was made by sputum cytology. The carcinoid cells had exfoliated into the sputum collected immediately after bronchofiberscopic examination although the bronchial tissues obtained at this time did not reveal any histological findings suggestive of neoplasia. The distinctive cytological features in sputum of atypical carcinoid that differentiate it from small cell carcinoma are considered to be the relatively abundant vesicular cytoplasm and the finely reticular or granular chromatin pattern observed in well-preserved tumor cells. The present case also suggests that clinical data may be indispensable to the differential cytological diagnosis of such tumors.