There were 83 cases of usual interstitial pneumonia (UIP) in 3712 cons
ecutive autopsy cases during 1972 to 1992 in Toranomon Hospital. Prima
ry lung cancer had arisen in 40 cases of UIP in that period. The preva
lence of lung cancer (48.2%) in UIP was significantly higher than that
of lung cancers (9.1%) in the age-matched general population without
UIP (P < 0.001). The prevalence of association of multiple lung cancer
in UIP (20.0%) was also significantly increased. Thus, UIP showed a r
emarkable potency to develop lung cancers. The lung cancer cases in UI
P had obvious smoking habits. Both the rates of smokers and the quanti
ty of smoking were significantly increased in the lung cancer cases in
UIP (P < 0.05). There was a distinct anatomical distribution of lung
cancer in UIP. Most cancers in UIP (98%) arose in the peripheral area
of the lung (P < 0.001, compared to lung cancer cases without UIP) wit
h close relation to the honeycombing lesion. Studies on surgical speci
mens with small cancers showed that most tumors in UIP arose in the bo
rder area between honeycombing and the non-fibrotic area. Thus, the fr
ont of the remodeling of the lung is suspected to be a potential field
of developing lung cancer, The chronic inflammatory process resulting
in the remodeling of the lung may play an important part in the devel
opment of lung cancer in UIP under the circumstance of heavy smoking.