Validation of Napsin A/TTF-1 Double Stain in Adenocarcinoma of the Lung Versus Malignant Mesothelioma.
Andras Khoor, Cherise Cortese, Philip T Cagle. Mayo Clinic, Jacksonville, FL; The Methodist Hospital, Houston, TX
Background: Double staining can be performed using two antibodies and a single detection system, if the target antigens are located in different cellular compartments. This can result in cost savings. TTF-1 is a well established pulmonary adenocarcinoma marker; recent studies have indicated that Napsin A may also have a role in separating adenocarcinoma of the lung from malignant mesothelioma. TTF-1 is a nuclear stain, whereas Napsin A shows granular cytoplasmic reactivity.
Design: The objective of this study was twofold: (1) to confirm a role for Napsin A in separating adenocarcinoma of the lung from malignant mesothelioma and (2) to validate the use of Napsin A and TTF-1 as a double stain. Tissue microarrays composed of 114 cases of pulmonary adenocarcinoma and 46 cases of epithelioid malignant mesothelioma were available for the study. Immunohistochemistry was performed using a mouse monoclonal Napsin A antibody (Leica, Newcastle, UK), a mouse monoclonal TTF-1 antibody (Dako, Carpinteria, CA), and the NovoLink Polymer Detection System (Leica) with DAB as the chromogen. The primary antibodies were applied both individually and as a cocktail (double stain).
Results: The 114 pulmonary adenocarcinoma cases stained as follows:
|Single staining method||Double staining method|
|Napsin A +||92 (80%)||92 (80%)|
|TTF-1 +||95 (83%)||95 (83%)|
|Napsin A + and/or TTF-1 +||98 (86%)||98 (86%)|