Molecular subgroups of small (pT1) breast carcinomas belonging exclusively to the ductal infiltrating variety.
BACKGROUND
The use of microarray technology has resulted in a new classification of breast cancer according to gene expression profiles. None of the reports published so far using this new classification has stratified the studied tumors by histology or size.


METHODS
This study was restricted to the ductal infiltrating variety only, and to pT1 size using the immunohistochemical markers estrogen receptor (ER), progesterone receptor (PR), HER2 and cytokeratin 5/6. ER+ and/or PR+, HER2- tumors were termed "luminal A"; ER+ and/or PR+, HER2+ "luminal B"; triple-negative, CK 5/6+ and/or HER1+ "basal-like"; with an additional category for ER-, PR-, HER2+ tumors termed HER2, and a final group of unclassified ones, negative for all five markers.


RESULTS
Out of 346 tumors, 251 (72.5%) were luminal A, 45 (13%) were "triple-negative" ("basal"-like), 20 (5.8%) were luminal B, and 30 (8.7%) were HER2. Luminal A, "triple-negative" ("basal"-like), and HER2-expressing tumors (luminal B + HER2) showed significantly different associations with histological and nuclear grade, mutant p53 expression and Ki67 labelling index.


CONCLUSIONS
Studies of the other, less frequent histological varieties of breast cancer, stratifying by tumor size, are mandatory to disclose which precise gene-expression pattern defines similar subgroups.
Schneider
José
J
Centro de Patologia de la Mama, Universidad Rey Juan Carlos, Facultad de Ciencias de la Salud, Alcorcon, Madrid, Spain. jose.schneider@urjc.es
Tejerina
Armando
A
Perea
Clemente
C
Lucas
Raúl
R
Sánchez
Jaime
J
D001943:Breast Neoplasms / Q000145:classification* / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000145:classification* / Q000473:pathology*; D004847:Epithelial Cells / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D053555:Keratin-5 / Q000378:metabolism; D053553:Keratin-6 / Q000378:metabolism
D053555:Keratin-5; D053553:Keratin-6