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Do the myoepithelial markers p63, Calponin and Smooth Muscle Myosin improve the interpretation of breast core needle biopsies.
Louise Castelluccia MSc.BSc (Hons), AIBMS, Pathology Department, Crosshouse Hospital, Kilmarnock, Ayrshire
Dr.A.W.Milne MRC Path, Consultant Pathologist, Pathology Department, Crosshouse Hopital, Kilmarnock, Ayrshire
INTRODUCTION
Breast Cancer is the commonest cancer in women and comprises 23% of all female cancers. Studies in the UK have shown that approximately 40,000 women are diagnosed with breast cancer every year with an annual mortality of approximately 13,000. Breast Cancer affects one woman in nine at some time in her life and is the most widespread cancer in the world today.
Over the last few years there has been an increase in the utilisation of core needle biopsies as a preoperative assessment of breast lesions. A wide variety of breast lesions present with challenging diagnostic problems especially when the lesions are represented as a small proportion in core needle biopsies (CNB). Most breast lesions can be diagnosed accurately on the evaluation of Haematoxylin and Eosin stain alone but sometimes the Pathologist can have difficulties in making a definitive diagnosis because of the overlapping features of some benign and malignant lesions as well as similar morphologies.
The identification of a myoepithelial cell (MEC) layer by immunohistochemistry is a valuable diagnostic indication in distinguishing benign and in situ neoplasms, where MEC layer is present, from invasive carcinoma in breast where MEC layer is absent.
Immunohistochemistry (IHC) markers are now used routinely to aid the pathologist in diagnosis with difficult cases and to differentiate benign and in situ carcinoma from invasive carcinoma. In the past, researchers used antibodies to basement membranes, such as laminin and collagen VII to detect stromal invasion as well as other MEC markers anti-S100 and anti-CD10.
MEC markers currently used in our laboratory are Cytokeratin 5/6 (CK5/6) and Smooth Muscle Actin (SMA) but make interpretation of breast lesions difficult for Pathologists due to background staining and other factors.
Three newly identified proteins that may function as highly specific myoepithelial markers are Calponin, Smooth Muscle Myosin (SMM) and p63.
AIMS
To determine whether the commercially available myoepithelial markers Calponin, Smooth Muscle Myosin (SMM) and p63 improve the interpretation of breast core needle biopsies in our laboratory compared with SMA and CK5/6, which are currently used
To establish the optimum panel of MEC markers for interpretation and diagnosis of breast cancer in CNBs
METHOD
This was a retrospective study on 69 consecutive breast core needle biopsies previously obtained and diagnosed during 2003. The archival tissue samples were fixed in 10% Neutral Buffered Formalin (NBF) for a minimum of 12 hours before being processed to wax on the Peloris Tissue Processor. 29 cases of invasive carcinoma and 40 cases of non-invasive lesions were identified. Seven serial paraffin wax sections were cut at 4um, six of which were lifted onto superfrosted white slides for immunohistochemistry and the final section was stained with Haematoxylin and Eosin (H&E). Sections from each case were immunostained with p63, Smooth Muscle Myosin (SMM), CK5/6, Smooth Muscle Actin (SMA) and Calponin using the DAKO ChemMate EnVision Polymer-Enhanced 2 step method and visualised with 3,3'Diaminobenzidine tetrahydrochloride (DAB).
Reactivity of each antibody was scored separately on basis of 4 variables: MEC layer; background stromal myofibroblasts; blood vessels; epithelial cells. Staining of the sections was recorded using following scoring system shown in Table 1.
Table 1
Intensity of Staining
0
Negative
1
Weak
2
Moderate
3
Strong
Appearance of Staining
F
Focal
D
Discontinuous
C
Circumferential
L
Lifted
The variable stromal myofibroblasts surrounding acini was only scored for invasive cases. If there was benign tissue present on any of the invasive sections then the MEC layer was scored and included as non-invasive case. A percentage of the immunostaining intensities for each variable were calculated for SMA, CK5/6, Calponin, SMM and p63. The percentage of staining appearances of the MEC layer for each antibody was calculated out of the 69 non-invasive breast cases. A percentage was also calculated for the staining intensity of stromal myofibroblasts surrounding invasive acini our of the 29 invasive breast cases for each antibody.
Continued here
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