[254] Reevaluation and Identification of the Best Immunohistochemical Panel for Differentiating Breast Ductal Adenocarcinoma from Pancreatic Adenocarcinoma

H Liu, J Shi, JW Prichard, F Lin. Geisinger Medical Center, Danville, PA

Background: When working on an unknown primary, differentiation of adenocarcinoma of the pancreas from ductal carcinoma of the breast can be challenging. Estrogen receptor (ER) is considered as the best marker in this regard; however, only about 70% of ductal carcinoma of the breast may be positive for ER and the positive rate is much lower in high grade ductal carcinomas. Many tumor-associated markers have been reported to be useful in this regard; however, the reproducibility of these markers has not been tested and confirmed in one system. This study investigates the utility of 15 different immunohistochemical markers in the distinction of ductal carcinoma of the breast from pancreatic adenocarcinoma.
Design: We immunohistochemically evaluated the expression of 1) epithelial markers (CK17, CK19, CK903), 2) mucin gene products (MUC1, MUC2, MUC4, MUC5AC, MUC6), 3) tumor suppressor genes and transcription factors (ER, PR, Dpc4/SMAD4), and 4) tumor-associated proteins (KOC, maspin, CA19-9, GCDFP-15) on 70 cases of ductal carcinoma of the breast (40 grade II cases and 30 grade III cases) and 70 cases of pancreatic adenocarcinoma on tissue microarray sections. The staining intensity was graded as weak or strong. The distribution was recorded as negative (<5% of tumor cells stained), 1+ (5-25%), 2+ (26-50%), 3+ (51-75%), or 4+ (>75%).
Results: ER was positive in 75% of grade II ductal carcinomas; but it was only positive in 18% of grade III ductal carcinomas. The immunostaining results are summarized in Table 1.

Table 1. Summary of the Immunohistochemical Staining Results
MarkersPancreatic Adenocarcinoma (N=70)Breast Ductal Carcinoma (N=70)

Conclusions: Our data demonstrate that KOC, ER, CK17 and MUC5AC are an effective antibody panel in the distinction of pancreatic adenocarcinoma from ductal carcinoma of the breast. In addition, Dpc4/SMAD4, CA19-9, MUC4, and maspin may have some utilities as well.
Category: Breast

Monday, March 22, 2010 1:00 PM

Poster Session II # 51, Monday Afternoon


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