DIFFERENTIATION OF DESQUAMATIVE INTERSTITIAL PNEUMONIA (DIP) FROM PULMONARY ADENOCARCINOMA BY IMMUNOCYTOCHEMISTRY

Aim: After a misdiagnosis of pulmonary adenocarcinoma as desquamative interstitial pneumonia (DIP), we investigated whether immunohistochemi cal markers could differentiate these conditions. Methods and results: Three cases of DIP and one pulmonary adenocarcinoma masquerading as D IP were studied by light and electron microscopy, All cases were mucin -negative. The cases of DTP were CD68 positive but cytokeratin-negativ e. The adenocarcinoma was cytokeratin-positive (AE1/3 and CAM5.2), as well as showing some CD68-positive cells. Markers for carcinoma (CEA, Ber-EP4, and Leu M1) were negative in all cases. Ultrastructurally the adenocarcinoma appeared to be derived from Type II pneumocytes. Concl usion: Before a diagnosis of DIP is made, cytokeratin markers should b e used.