[214] Invasive Lobular Carcinomas Do Not Express Basal Cytokeratin Markers CK5/6, CK14 and CK17

N Khilko, J Wang, DG Hicks, P Tang. University of Rochester Medical Center, Rochester, NY; RTI Health Solutioon, Research Triangle Park, NC

Background: Basal subtype of ductal carcinomas been shown to be associated with high grade tumors and poor clinical outcome. Pervious study has shown that basal markers CK5/6 can be detected in up to 17% of invasive lobular carcinomas (ILC). Here we studied the expression of three basal cytokeratin markers (CK5/6, CK14, and CM17) in ILC.
Design: Fifty-three ILC were identified from the files of Department of Pathology. Clinical and pathological information including patients' age, tumor size, multifocality, ER, PR and HER2 status, lymphovascular invasion, perineural invasion, and status of lymph nodes were reviewed and recorded. One representative section from each case was also stained with antibodies to basal markers CK5/6, CK14 and CK17, and luminal markers CK8 and CK18. Any strong cytoplasmic stain was considered as positive.
Results: Among the 53 cases of ILC, 42 were classic lobular carcinomas, 6 were tubular-lobular carcinoma, and 5 were pleomorphic lobular carcinomas. There was no significant difference among these three groups in patients' age, tumor size, uni- or multifocality, expression of ER and PR, lymphovascular invasion, perineural invasion and lymph node metastasis. The only statistically different factor was HER2 over-expression, which was only observed in pleomorphic ILC (p=0.0073). None of the 53 cases was positive for any of the three basal cytokeratin markers. 51/53 cases expressed luminal cytokeratin markers CK8 and CK18, and the two negative cases were both ER and PR positive classical ILC.
Conclusions: All three basal CK markers failed to show expression in any of ILC in the current study, suggesting that very few cases of ILC will demonstrate a basal phenotype. More studies are needed to further investigate molecular classification in lobular lesions.
Category: Breast

Wednesday, March 11, 2009 1:00 PM

Poster Session VI # 22, Wednesday Afternoon