[466] The Utility of Napsin-A in the Identification of Primary and Metastatic Lung Adenocarcinoma among Cytologically So-Called "Poorly Differentiated Carcinomas"

LM Stoll, E Gabrielson, DP Clark, QK Li. Johns Hopkins Hospital, Baltimore, MD

Background: Cytologic sampling of lesions plays a critical role in the diagnosing and staging of lung cancer, particularly in patients with advanced disease (stage III and IV). Currently, medical treatments for non-small cell lung carcinoma have advanced to the point at which further delineation of adenocarcinoma versus other carcinoma is necessary. Although lung adenocarcinoma can be differentiated and diagnosed in most of the cytological cases, a significant number of cases are still difficult to classify due to a variety of reasons. Napsin-A has recently come to attention as a potential marker of lung adenocarcinoma. Only a few studies have investigated the role of Napsin-A in daily cytology practice. In this study, we have investigated the utility of Naspsin-A, and compared its sensitivity with TTF-1, in the identification of lung adenocarcinoma from so-called “poorly differentiated carcinoma”.
Design: A computer search of a large teaching hospital identified 41 cytology cases of "poorly differentiated carcinoma," each having adequate cell block material for immunohistochemical staining and surgical follow-up confirming poorly differentiated adenocarcinoma of the lung. Cases consisted of metastatic (n=24) as well as primary lung (n=17) lesions. Sites of metastasis included neighboring lymph nodes (n=15); pleural fluid (n=5); liver/other (n=4). Cases were subsequently stained for TTF-1 and Napsin-A. Staining characteristics were then correlated to determine the sensitivity of the immunostains for identification of lung adenocarcinoma.
Results: Concordant results were seen in 38/41 (93%) of cases. Among primary lung adenocarcinomas TTF-1 and Napsin-A were positive in 10/17 (59%) and 9/17 (53%) respectively, while 7/17 (41%) cases were negative for both markers. Within metastatic lung adenocarcinomas, TTF-1 and Napsin-A were positive in 17/24 (71%) and 15/24 (63%) respectively, with 6/24 (25%) cases negative for both markers. The overall sensitivity of TTF-1 was 66%, while Napsin-A was 59%.
Conclusions: TTF-1 remains a superior marker, as compared to Napsin-A, for the identification of primary and metastatic pulmonary adenocarcinomas, including those designated as poorly differentiated. However, as Napsin-A closely correlates with TTF-1 staining, it may be used as an accompanying marker in cytopathologic diagnosis, particularly in those difficult cases.
Category: Cytopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 48, Wednesday Afternoon


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