A case of bronchial squamous cell carcinoma in situ detected by sputum cytology.

A 64-year-old man underwent a medical checkup in May 1996 and was evaluated as class V using sputum cytology. Chest X-ray examination, bronchoscopy and chest computed tomography (CT) demonstrated no abnormalities. Thereafter, the patient was followed up with chest X-ray, bronchoscopy and chest CT at 3-month intervals. In December 1996, chest CT showed an increased density at the mediastinal side of the left upper bronchus, B1+2. There were no findings on bronchoscopy, but subsequent exfoliative cytology demonstrated keratinized malignant cells in samples obtained from left upper bronchus, B1+2. Although, it was difficult to identify localization of the tumor, left upper lobectomy was performed and the diagnosis of squamous cell carcinoma in situ was finally made. Here, we report on the course of this patient and discuss the diagnostic usefulness of sputum cytology as well as the pathogenesis of lung squamous cell carcinoma.