TTF-1 and Napsin-A Double Staining in Lung Adenocarcinoma: Diagnostic Utility in Fine Needle Aspirations.
Nazneen Fatima, Cynthia Cohen, Momin T Siddiqui. Emory University Hospital, Atlanta, GA
Background: Lung cancer is the most common type of cancer in terms of mortality worldwide. Recent FDA approval of Avastin in the treatment of non-squamous cell lung cancer and its contraindication in squamous cell carcinoma (SQCC) has made it crucial to accurately diagnose the different types of non-small cell lung cancers. Immunohistochemistry (IHC) for thyroid transcription factor-1 (TTF-1) is widely used in the diagnosis of lung adenocarcinomas (ADC). It is positive in approximately 75% of lung ADC and negative in most SQCC and ADC of other organs. A new promising marker, Napsin-A, has been detected in the cytoplasm of type 2 pneumocytes and alveolar macrophages. It is an aspartic proteinase involved in the processing of surfactant protein B and is strongly positive in up to 80% of primary lung ADC by IHC. Small cell carcinomas and SQCC of the lung have been shown to be negative for Napsin-A. A combination (Double stain) of these two stains (TTF-1 and Napsin-A) has been proposed to achieve higher sensitivity and specificity.
Design: FNA cell blocks of 36 lung ADC and 26 lung SQCC were studied. IHC was performed on formalin-fixed paraffin-embedded cell blocks. Expression of Napsin-A as cytoplasmic red stain and TTF-1 as nuclear brown stain were identified easily. For positive control, lung ADC was used.
|TTF-1/Napsin-A Double stain||TTF-1 Alone||Napsin-A Alone|
|ADC||27/36 (75%)||4/36 (11%)||4/36 (11%)|
|SQCC||3/26 (11%)||6/26 (23%)||0/26 (0%)|
|TTF-1/Napsin-A Double Stain||75%||88%||90%||71%||80%|