A subset of in situ breast tumor cell clusters lacks expression of proliferation and progression related markers but shows signs of stromal and vascular invasion.
BACKGROUND
Our previous studies in pre-invasive mammary tumors revealed that estrogen receptor negative cell clusters (ER NCC) overlying focally disrupted myoepithelial (ME) cell layers showed a significantly higher rate of genetic abnormalities and cell proliferation than adjacent cells without ME cell layer disruptions. A subset of these ER NCC, however, completely lacked expression of Ki-67, a most commonly used marker for cell proliferation. The purpose of this study was to further elucidate the immunohistochemical and morphological profiles of these ER NCC.


METHODS
Fifteen cases with such ER NCC were selected from our previous studies and assessed with a panel of commonly used biomarkers for cell proliferation, tumor progression, and normal stem cells.


RESULTS
Immunohistochemically, in addition to Ki-67 and ER, these ER NCC completely lacked expression of all other proliferation and progression related markers that were distinctly expressed in adjacent cells within the same duct but overlying the non-disrupted ME cell layer. These ER NCC also lacked expression of all normal stem cell-related markers tested. These cell clusters, however, showed a higher and atypical expression of c-erb-B2, compared to their adjacent counterparts. Morphologically, these ER NCC were generally arranged as triangle shaped structures penetrating into the stroma, similar to micro-invasive lesions. About 15% of these ER NCC appeared to directly spread into blood vessel-like structures. These ER NCC and their possible derivatives within the stroma and blood vessels-like structures shared the same morphologic and immunohistochemical features. No comparable ER positive cell clusters were identified in any of the cases.


CONCLUSIONS
These findings suggest that these ER NCC and their possible derivatives are likely regulated by yet to be defined molecules and mechanisms, and they are unlikely to respond to currently available anti-mitotic agents.
Man
Yan-Gao
YG
Department of Gynecologic and Breast Pathology, Armed Forces Institute of Pathology and American Registry of Pathology, 6825 16th Street, NW, Washington, DC 20306-6000, USA. man@afip.osd.mil
Shen
Ting
T
Weisz
Judith
J
Berg
Patricia E
PE
Schwartz
Arnold M
AM
Mulshine
James L
JL
Sang
Qing-Xiang Amy
QX
Nieburgs
Herbert E
HE
D014408:Biomarkers, Tumor / Q000032:analysis*; D001943:Breast Neoplasms / Q000737:chemistry* / Q000473:pathology*; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000737:chemistry* / Q000473:pathology*; D049109:Cell Proliferation; D018450:Disease Progression; D004847:Epithelial Cells / Q000737:chemistry / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000032:analysis; D009361:Neoplasm Invasiveness; D011960:Receptors, Estrogen / Q000032:analysis; D017154:Stromal Cells / Q000737:chemistry / Q000473:pathology; D014407:Tumor Cells, Cultured
D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen; D011960:Receptors, Estrogen