[Roles of immunohistochemistry in prognostic assessment of basal-like breast cancer].

OBJECTIVES: Basal cell-like breast cancer is one of the subtypes using molecular typing, and this subtype attracted a wide spread attention. Currently, no uniform diagnostic criteria are available. Most studies demonstrated poor outcomes, but contradictory conclusions appeared recently. The prognosis of basal cell-like breast cancer using different immunohistochemical criteria were analyzed.

METHODS: Two hundred and eighty-four invasive breast cancers with a follow-up information over 5 years were evaluated for ER, PR, HER2, CK5/6, CK14, EGFR expression on tissue microarray immunohistochemically. Based on the results, these cases using four different diagnostic criteria were categorized, namely: Nielsen (ER-/HER2-, CK5/6+ and/or EGFR+), Kim (ER-/PR-/HER2-, CK5/6+ and/or CK14+ and/or EGFR+), Triple-negative (ER-/PR-/HER2-), and basal-CK (CK5/6+ and/or CK14+). 5-year survival information was compared between groups.

RESULTS: The prevalence of basal cell-like breast cancer by Nielsen, Kim, Triple-negative and basal-CK were 15.5% (44/284), 14.8% (42/284), 43.3% (123/284) and 21.1% (60/284) respectively; the recurrence rates were 18.2% (8/44), 21.4% (9/42), 10.6% (13/123) and 11.7% (7/60) respectively. These were higher than recurrence rates for other subtypes, but only the differences by Nielsen's and Kim's criteria were significant. Using Nielsen's and Triple-negative's criteria, basal-like tumors showed shorter 5-year disease-free survival (both P < 0. 01) and overall survival (P < 0.05 and 0.01) than luminal A subtype, using Kim's criteria, basal-like tumors showed a lower 5-year disease-free but not overall survival than luminal A subtype (P < 0.01); no significant difference was found on 5-year survival between basal-like and non-basal-like tumors when typed by basal-CK.

CONCLUSION: Basal cell-like breast cancers are more likely to show more recurrence and worse outcome, but different immunohistochemical diagnostic criteria have an influence on their prognostic analysis, so a uniform diagnostic criteria is essential for the further study of basal-like breast cancers.