Immunohistochemical Analysis of Napsin A in 77 Lung Carcinomas and 509 Non-Pulmonary Malignancies
ME Arcila, N Rekhtman, J Teruja-Feldstein. Memorial Sloan Kettering Cancer Center, New York, NY
Background: Napsin A is an aspartic proteinase recently reported to be expressed in the majority of lung adenocarcinomas (AD) with sensitivity superior to that of TTF-1. Napsin A is normally expressed only in type II pneumocytes and proximal renal tubules. In addition, expression in B-lymphocytes has been reported in animal models. Immunohistochemistry (IHC) for Napsin A has been proposed as a useful ancillary tool in the identification of lung origin in carcinomas of unknown primary. However, the specificity of Napsin A has not been fully evaluated.
Design: We performed IHC on tissue micro-arrays (TMA) constructed form of 50 lung AD, 23 lung squamous cell carcinomas, 4 lung neuroendocrine neoplasms, 160 colon AD, 81 gastric AD, 29 cervical AD, 52 endometrial adenocarcinomas, 57 breast adenocarcinomas, 50 clear cell renal cell carcinomas, 46 papillary renal cell carcinomas, and 34 marginal zone lymphomas. IHC was scored based on intensity of cytoplasmic staining as 1+ (faint), 2+ (moderate), or 3+ (strong). The scores of 2+ or 3+ were considered positive.
Results: Napsin A was positive in 37 of 50 (74%) lung AD, and 13 of 46 (28%) papillary renal cell carcinomas. All pulmonary squamous cell carcinomas, neuroendocrine neoplasms and all non-pulmonary malignancies were negative for Napsin A. Strong reactivity was also found in type II pneumocytes and renal tubular cells.
Conclusions: We confirm previous reports that Napsin A shows robust expression in the majority of lung AD and in a subset of papillary renal cell carcinomas. In addition, this study represents the largest screen of non-pulmonary carcinomas for Napsin A expression, revealing that no other tested extra-pulmonary malignancy had reactivity for Napsin A, confirming Napsin A as a highly specific marker of a lung or renal origin.
Wednesday, March 24, 2010 9:30 AM
Poster Session V # 244, Wednesday Morning