Cytokeratin 7 & 20: Does the Classic Teaching Hold True in Triple Negative Breast Cancers?
Simone M Davion, Kalliopi P Siziopikou, Megan Sullivan. Northwestern University, Chicago, IL
Background: The term “breast cancer” (BC) encompasses a heterogenous group of tumors that includes triple negative carcinomas (TNC). As molecular differences within BC were described, it became evident that some TNC expressed a different cytokeratin (CK) profile. However, much of the immunohistochemical (IHC) studies on BC that are still cited today were performed prior to these discoveries. The aims of this study were to: 1) determine if the classic differential CK profile for BC (CK7+/CK20-) holds true in TNC; 2) see if CK 5/6+ TNC is associated with aberrant CK expression.
Design: After IRB approval, the pathology database was reviewed for TNC and 99 cases were selected. Relevant patient and pathologic staging data were recorded. Tissue miroarrays (TMA) with 0.2 cm cores were made with TNC in triplicate and control tissue. TMAs were stained with CK7 (DAKO OV-TL12/30), CK20 (DAKO Ks208) & CK5/6 (DAKO DS/16B4). The CK 7 & 20 IHC was interpreted as follows: positive (>90% of tumor cells stain), patchy (10-90%), focal (<10%) & negative (<1%). The CK 5/6 was called either positive (any staining) or negative
Results: The average age of our TNC cohort was 54.6 (range 32-93). The average tumor size was 2.8 cm and 50% had involved lymph nodes. Of the 99 patients included in the TMA, one was dropped from the final analysis due to tissue loss. 76 of the TNC showed strong diffuse positivity with CK7 (78%). The remaining 22 TNC showed patchy to negative results (see table 1). As expected, the vast majority of TNC were CK20 negative but 5 (5.1%) were positive with 3 of these showing a diffuse staining pattern. No TNC were CK7-/20+. 53% of the TNC were positive for CK 5/6. However, CK 5/6 positivity did not predict an aberrant CK 7 & 20 staining pattern (3/5 dual positive cases and 1/2 dual negative cases were CK 5/6 positive) Of the 7 patients whose TNC showed a “non-classic” 7/20 pattern, no difference in age, race, tumor characteristics or staging was identified.
|CK 7 STAINING PATTERN||NUMBER OF CASES||% OF CASES|