Synchronous bilateral double primary lung cancer associated with diffuse interstitial fibrosing pneumonitis (DIFP).

Double primary lung cancer with diffuse interstitial fibrosing pneumonitis (DIFP) was detected in a 61 year-old man at autopsy. Histologically, alveolar septa in whole lobes of right and left lungs were thickened diffusely with fibrosis, edema, and inflammatory cell infiltration. Alveolar cavities contained fibrinous exudate. A tumor mass measuring 8 X 5 X 5 cm occupying the right hilar portion was epidermoid carcinoma involving the right superior lobar bronchus and hilar lymph nodes. There were no metastatic foci in the right middle and lower lobes. In the lower lobe of the left lung, scattered foci of bronchiolo-alveolar carcinoma and those of epidermoid carcinoma coexisted. There were no metastatic foci in the left upper, lower lobes, and hilar lymph nodes. Both atypical bronchiolar epithelial proliferation associated with bronchiolo-alveolar carcinoma and squamous metaplasia associated with epidermoid carcinoma were detected at the same time. The clinical and pathological characteristics among 81 reported cases of lung cancer associated with DIFP are reviewed.