[141] Cytokeratin Immunohistochemical Profile of Breast Cancer: Do CK7 Negative Breast Carcinomas Exist?

Esther Elishaev, Rohit Bhargava. Magee Women's Hospital of UPMC, Pittsburgh, PA

Background: Often the first step in immunohistochemical (IHC) evaluation of a carcinoma of unknown origin is the tumor's CK7/CK20 profile. Breast cancers are categorize as tumors showing a CK7+/CK20- IHC profile. Any other profile will sway the investigator into a different direction.
Design: In order to identify other possible profiles, 186 consecutive primary breast carcinomas were investigated. The study was performed on tissue microarrays with 3 fold redundancy in order to mimic small core biopsies that are often the specimen a pathologist receive for analysis. A detailed IHC scoring using an H-score method (score ranges from 0 to 300) and also percentage of positive cells was utilized for evaluating CK7 (clone OVTL-30) and CK20 (clone 30S) stains. A biotin block was used during IHC procedure to block any non-specific staining.
Results: The most common IHC profile of breast carcinoma is CK7+/CK20- seen in 173/186 (93%) cases, followed by CK7-/CK20- profile identified in 12/186 (6.5%) cases. Only one case (0.5%) showed a CK7+/CK20+ profile, and none of the cases showed a CK7-/CK20+ profile. Most CK7+ cases were strongly and diffuse positive with a mean and median H-scores of 260 and 290 respectively with standard deviation of 67. The CK7 results with respect to percentage positive cells and receptor status is shown in table 1. In the only CK+/CK20+ case, CK20 reactivity was weak and was seen in 15% of the cells.

Percentage of CK7+ cells with respect to receptor status
 0% cells+1-10%cells+11-50%cells+>50% cells+Total

Conclusions: Although majority of breast carcinomas are CK7+/CK20-, an unusual profile (i.e. CK7-/CK20-) is not uncommon and can create confusion in investigation of a carcinoma of unknown primary. Fortunately, many of the CK7 negative tumors are hormone receptor positive. The results of this study strongly support the use of IHC panels when investigating tumors of unknown primary origin.
Category: Breast

Wednesday, March 21, 2012 9:30 AM

Poster Session V # 41, Wednesday Morning


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