Histologic grading in breast cancer is based on the evaluation of 3 morphologic features (tubule formation, nuclear pleomorphism and mitotic count), is essentially describing proliferation and differentiation in breast cancer, and is considered an important prognostic factor for this disease. It has been suggested that histologic grade 1 and 3 breast tumors are 2 different diseases that may have distinct molecular origins, pathogenesis and natural history. Different single markers like Ki-67, thymidine labeling index and S phase fraction/flow cytometry have been studied as markers of proliferation, but none of them, with the possible exception of Ki-67, is currently employed routinely in clinical practice. The advent of the powerful microarray technology has enabled scientists to comprehensively study proliferation in breast cancer on a genome-wide scale. A gene expression grade index (GGI) was developed that challenges the existence and clinical relevance of an intermediate grade 2 classification. The GGI could reclassify patients with histologic grade 2 tumors into 2 groups with high versus low risks of recurrence. GGI has also been used to define 2 clinically relevant subgroups in estrogen receptor-positive breast carcinomas. Finally, in the largest meta-analysis of publicly available gene expression and clinical data, 4 stable molecular subgroups of breast cancer have been identified, namely ER–/HER–, HER2+ and ER+/HER2–, which was divided into 2 subgroups (ER+/low proliferation and ER+/high proliferation). In this same meta-analysis, proliferation was shown to be the common driving force responsible for the performance of various breast cancer prognostic signatures.

Keywords:
Histologic grading, Breast cancer, Gene expression grade index, Gene profiling, Proliferation
This content is only available via PDF.
© 2008 S. Karger AG, Basel
2008
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.