1. ¹Department of Pathology, Singapore General Hospital, Singapore
2. ²Department of General Surgery, Singapore General Hospital, Singapore
3. ³Duke-NUS Graduate Medical School, Singapore
4. ⁴Genome Institute of Singapore, Singapore

Correspondence: Dr PH Tan, FRCPA, Department of Pathology, Singapore General Hospital, Outram Road, Singapore 169608, Singapore. E-mail: gpttph@sgh.com.sg

Received 20 July 2009; Revised 3 September 2009; Accepted 8 September 2009; Published online 23 October 2009.

Abstract

Triple-negative breast cancer, defined as that with negative expression of estrogen and progesterone receptors and cerbB2, accounted for 11% of invasive breast cancers in our study, drawn from an original cohort of 7048 women diagnosed with breast cancer from the files of the Department of Pathology, Singapore General Hospital, over 14 years. Women with triple-negative breast cancer were generally postmenopausal, with adverse pathological characteristics of high histological grade and frequent nodal metastases. Using a set of 61 invasive breast cancers earlier profiled into molecular subtypes with expression arrays, we defined specificity and sensitivity values for different immunohistochemical panels of basal keratins (CK5/6, CK14, CK17, 34E12), CD117, EGFR, p63 and SMA in defining basal-like breast cancer. Subsequent application of a tri-panel of CK14, EGFR and 34E12 (specificity 100% and sensitivity 78%) to our group of 653 triple-negative breast cancers delineated 84% to be basal-like. Immunohistochemical expression of individual biological markers correlated with unfavorable pathological parameters. We conclude that triple-negative breast cancers in an Asian population harbor adverse pathobiological features, and an immunohistochemical surrogate panel can be reliably used to define basal-like cancers among them.