Evaluating the utility of trefoil factor 1 as a mammary-specific immunostain compared and in conjunction with GATA-3 and mammaglobin in the distinction between carcinoma of breast and lung.

OBJECTIVES: The distinction between metastatic breast carcinomas (BCs) and primary lung carcinomas (PLCs) can be difficult. This study tested the utility of trefoil factor 1 (TFF1) for this purpose and compared it with mammaglobin and GATA protein binding 3 (GATA-3). METHODS: Tissue microarrays containing 365 BCs and 338 PLCs were stained with TFF1, mammaglobin, and GATA-3, and an H-score was calculated. Sensitivity, specificity, and accuracy were calculated, and logistical regression analysis was performed. RESULTS: Accuracy of correctly classifying the tumor type was 81.9%, 71.3%, and 64.0% for GATA-3, mammaglobin, and TFF1, respectively. Odds ratios for selecting BCs were 25.69, 93.15, and 4.17, respectively, with P values less than .001. With a single exception, the best immunopanel included GATA-3 and mammaglobin in all comparisons. CONCLUSIONS: TFF1 demonstrated breast specificity but was inferior to mammaglobin and GATA-3. Therefore, its routine clinical use may not be justified. TFF1 showed little benefit when added to an immunopanel.