Significance of the histological and ultrastructural features of elastic fibers in diagnosis of bronchioloalveolar carcinoma.

OBJECTIVES The accurate identification of bronchioloalveolar carcinoma (BAC) from adenocarcinoma (AC) and other types of lung cancer is important from clinical perspectives; especially, when BAC is histologically-mixed with AC. We hypothesized that the elastic fibers (EF) pattern could be used as a differential marker to identify BAC from other lung cancers. The aim was to characterize the EF pattern in different types of lung cancer and evaluate its significance for differential diagnosis of BAC. PATIENTS AND METHODS Clinical samples of different types of lung cancers were collected. The samples were stained by hematoxylin-eosin (H&E) staining for histopathological comparison. Then, modified Weigert's staining of the EF was performed to characterize its patterns. The EFs were semi-quantified and compared among different types of lung cancer. Further, transmission electronic microscopy (TEM) was performed and ultrastructural features of the EFs were compared between BAC and adenocarcinoma (AC). RESULTS H&E staining histopathology could differentiate the most types of lung cancer except certain types, such as histologically-mixed BAC and AC. The EF pattern in BAC was uniquely different from other types of lung cancer as > 95% of BAC was + or ++ for EF staining while > 95% of other types of lung cancer were--or ± type. TEM study further confirmed the EF pattern difference between BAC and AC. CONCLUSIONS As the data show, as > 95% BAC specimens can be identified from other lung cancers based on EF (Weigert's) staining. The EF pattern in BAC is uniquely different from other types of lung cancer and, therefore, can be used as a differential clinical marker of BAC.