Abstract
Although it is well known that lung cancer frequently arises in cases of idiopathic interstitial pneumonia (IIP), there have been few report describing the topographical relationship between the primary site of lung cancer and honeycombing. The purpose of the present paper is to elucidate the precancerous state of IIP.
Fifteen autopsy cases of IIP associated with lung cancer and 8 autopsy cases of IIP without lung cancer were studied, with special regard to the topographical relationship between the primary site of lung cancer, honeycombing, squamous metaplasia, and the ratio of double lung cancer.
Although honeycombing of IIP invariably existed in the lower lobes, and more extensively than in other lobes, only 10 out of 20 lung cancers were found in the lower lobes. This appears to show that there is no lobal preferential site of lung cancer in cases accompanied by IIP. Of 10 double cancer-foci in 5 cases, however, 8 foci were present in the lower lobes. Thirteen out of 20 cancers were encased by or in close proximity to homeycombing. No dominant histologic type of lung cancers in IIP was noted, but there were 4 cases with atypical squamous metaplasia, 3 of which accompanied squamous cell carcinomas. There were 5 cases of double cancer in 15 cases of IIP with lung cancer, in contrast to 5 in 229 autopsy cases of lung cancer without IIP. The data strongly suggest that IIP is a precancerous state.
