Her2 negative luminal breast carcinoma and Ki-67 evaluation.
OBJECTIVE
To determine the degree of inter-observer variability in defining the percentage of Ki-67 immunohistochemical expression in breast carcinoma cases and to investigate the validity of using the cut-point of 14% for the administration of adjuvant treatment in luminal B (Her2 negative) carcinomas.


METHODS
99 ER, PR positive, Her2 negative breast carcinomas were consecutively selected from the Pathology files of "IASO" Women's Hospital. Ki-67 immunostaining was evaluated by four pathologists from four different institutions.


RESULTS
Concerning the whole study group, the inter-observer agreement was substantial. Subgroup analysis upon the cases were at least one observer evaluated Ki-67 as being less than 14% showed that the inter-observer agreement was reduced to fair. Further analysis revealed that both below and above the clinicopathological limit of 14%, stands a "grey zone" of about ±7%, in which inter-observer agreement is weak.


CONCLUSIONS
The administration of cytotoxic therapy in ER, PR positive, Her2 negative breast carcinomas featuring a Ki-67 labeling index of around 14, should be considered with caution. Probably decision-making should also take under consideration the whole morphological and biological profile of each tumor.
Pathology Department, National and Kapodistrian University of Athens, Athens, Greece.
Kitty
K
Pavlakis
Thomas
T
Vrekoussis
Anna
A
Tsipoura
Artemis
A
Tsenga
Petroula
P
Arapantoni-Dadioti
Theofani
T
Gavresea
Irini
I
Messini
Vassilis
V
Barbounis
D000970:Antineoplastic Agents / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D003661:Decision Support Techniques; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000378:metabolism*; D015588:Observer Variation; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D015203:Reproducibility of Results
D000970:Antineoplastic Agents; D019394:Ki-67 Antigen; D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human