[1784] Comparison of Napsin A and TTF-1 Expression in Metastatic Carcinomas from Various Sites: An Immunohistochemical Study of 143 Cases.

Sanjay Mukhopadhyay, Anna-Luise A Katzenstein. State University of New York Upstate Medical University, Syracuse

Background: TTF-1 is currently the best immunohistochemical marker of lung origin in metastatic adenocarcinomas of unknown primary. The aim of this study was to compare the utility of the novel marker napsin A to TTF-1 for the accurate identification of pulmonary origin in metastatic carcinomas.
Design: One hundred forty three metastatic carcinomas, including 54 adenocarcinomas of pulmonary origin and 89 carcinomas of non-pulmonary origin, were stained with antibodies to TTF-1 and napsin A. Non-pulmonary carcinomas included 57 adenocarcinomas and 32 other carcinomas that may enter the differential diagnosis of a metastatic pulmonary adenocarcinoma.
Results: The results are shown in Table 1.

Table 1. Napsin A and TTF-1 in 143 Metastatic Carcinomas
OriginNo. of casesNapsin A - pos (%)TTF-1 - pos (%)
LUNG5442 (78)44 (81)
NON-PULMONARY8911 (12)9 (10)
Colon1200
Breast1200
Kidney (RCC)115 (45)0
Thyroid*104 (40)9 (90)
Pancreas800
Urothelial tract (UC)600
Prostate600
Stomach500
Liver (HCC)51 (20)0
Esophagus500
Endometrium51 (20)0
Ovary400
RCC=renal cell carcinoma; *7 papillary, 2 medullary, 1 follicular; UC=urothelial carcinoma; HCC=hepatocellular carcinoma

The sensitivity and specificity of napsin A for adenocarcinomas of pulmonary origin were 78% and 88%, respectively. TTF-1 was 81% sensitive and 90% specific. Three metastatic adenocarcinomas of pulmonary origin were TTF-1-positive but napsin A-negative, while 1 was positive for napsin A but negative for TTF-1. In 2 additional adenocarcinomas of pulmonary origin, TTF-1 was weak and present only in rare cells whereas napsin A staining was strong and diffuse. The napsin A-positive endometrial tumor was a FIGO grade 2 endometrioid adenocarcinoma metastatic to a pelvic lymph node; the napsin A-positive tumor of hepatic origin was a well-differentiated hepatocellular carcinoma metastatic to the adrenal.
Conclusions: Napsin A is expressed in a wider variety of metastatic carcinomas than TTF-1. Its expression in endometrial adenocarcinoma and hepatocellular carcinoma has not been previously reported. Although the sensitivity and specificity of napsin A for metastatic pulmonary adenocarcinoma is slightly lower than TTF-1, occasional adenocarcinomas of pulmonary origin are negative or equivocal for TTF-1 but strongly positive for napsin A, suggesting that napsin A may have diagnostic utility in this setting.
Category: Pulmonary

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 270, Tuesday Morning

 

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