Clinical Study of 12 Cases of Roentgenologically Occult Lung Cancer

Of the 12 cases of roentgenologically occult lung cancer studied clinically, twowere double roentgenologically-occult cancer cases. All cases were rather elderly males and all were heavy smokers. The main detection factors included screening examinations for chromate workers (5 cases), complaints of bloody-sputum (4 cases) and cough (1 case) and further examinations of patients with other roentgenologically apparent lung cancers (2 cases). All cases were detected by means of bronchofiberscopic biopsy. Out of 14 lesions 4 were located in the lobar bronciii, 9 were in the segmental bronchi and 1 was in a subsubsegmental bronchus. Most lesions were located at bronchial orifices or bifurcations. The histologic type was squamous cell carcinoma in 9 cases, small cell carcinoma in 2 and adenocarcinoma in 1 case. The two small cell carcinoma cases were chromate workers. As for the question of multiple cancer, we had 5 cases of bilateral double lung cancer of which 2 were double X-ray-negative cancer cases. One case was synchronous and the other was asynchronous. Because of such multiplicity, care must be exercised in the diagnosis and the follow-up of X-ray-negative cases not to overlook the second cancer. Regarding treatment and prognosis, 8 cases were resected and 3 cases were only irradiated. In 2 resected cases, carcinoma recurred at the bronchial stump. On the other hand, the bilateral occult squamous cell cancers disappeared after irradiation therapy. Therefore in the treatment of X-ray-negative lung cancer, it is important to consider the histological type, multiplicity and the possible extension of carcinoma intothe proximal bronchi.