[368] 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.

Table 1:
 TTF-1/Napsin-A Double stainTTF-1 AloneNapsin-A Alone
ADC27/36 (75%)4/36 (11%)4/36 (11%)
SQCC3/26 (11%)6/26 (23%)0/26 (0%)

Table 2:
TTF-1/Napsin-A Double Stain75%88%90%71%80%

Conclusions: Double staining for TTF-1 and Napsin-A gives a sensitivity of 75% and specificity of 88% for ADC. An additional 8 ADC stained for either TTF-1 or Napsin-A. Utilizing this dual stain, lung ADC is diagnosed with an accuracy of 80%. We conclude that TTF-1/Napsin-A double stain is a better diagnostic technique than TTF-1 or Napsin-A alone, and helps in diagnosis of ADC with a positive predictive value of 90% and negative predictive value of 71%. Only 11% of SQCC stained with the double stain, an additional 23% with TTF-1 alone, but none for Napsin-A alone.
Category: Cytopathology

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 75, Tuesday Morning


Close Window