Interobserver Variability of Ki-67 Measurement in Breast Cancer

As measurement of Ki-67 proliferation index is an important part of breast cancer diagnostics, we conducted a multicenter study to examine the degree of concordance in Ki-67 counting and to find factors that lead to its variability. Thirty observers from thirty different institutions reviewed Ki-67-...

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Bibliographic Details
Published in:Journal of pathology and translational medicine 2016, 50(2), , pp.129-137
Main Authors: Chung, Yul Ri, Jang, Min Hye, Park, So Yeon, Gong, Gyungyub, Jung, Woo-Hee
Format: Article
Language:English
Subjects:
Automation
Breast cancer
Breast neoplasms
Cell cycle
Cell growth
Endocrine therapy
Estrogens
Gene expression
Immunoglobulins
Ki-67
Medical diagnosis
Multicenter
Observer variation
Original
Tumors
Working groups
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Summary:As measurement of Ki-67 proliferation index is an important part of breast cancer diagnostics, we conducted a multicenter study to examine the degree of concordance in Ki-67 counting and to find factors that lead to its variability. Thirty observers from thirty different institutions reviewed Ki-67-stained slides of 20 different breast cancers on whole sections and tissue microarray (TMA) by online system. Ten of the 20 breast cancers had hot spots of Ki-67 expression. Each observer scored Ki-67 in two different ways: direct counting (average vs. hot spot method) and categorical estimation. Intraclass correlation coefficient (ICC) of Ki-67 index was calculated for comparative analysis. For direct counting, ICC of TMA was slightly higher than that of whole sections using average method (0.895 vs 0.858). The ICC of tumors with hot spots was lower than that of tumors without (0.736 vs 0.874). In tumors with hot spots, observers took an additional counting from the hot spot; the ICC of whole sections using hot spot method was still lower than that of TMA (0.737 vs 0.895). In categorical estimation, Ki-67 index showed a wide distribution in some cases. Nevertheless, in tumors with hot spots, the range of distribution in Ki-67 categories was decreased with hot spot method and in TMA platform. Interobserver variability of Ki-67 index for direct counting and categorical estimation was relatively high. Tumors with hot spots showed greater interobserver variability as opposed to those without, and restricting the measurement area yielded lower interobserver variability.
ISSN:2383-7837
2383-7845
DOI:10.4132/jptm.2015.12.24