Breast cancer is the most common cancer affecting women in the world; it can only be life threatening when it becomes invasive. Disappearance of myoepithelial cell layer, degredation of basement membrane and extra cellular matrix due to altered expression of matrix degrading enzymes like (MMP2) is a prerequisite for tumor invasion. Aims of study : 1-To study the immunohistochemical reaction pattern of the myoepithelial cells in normal ,benign and malignant breast lesion using panel of MEC marker (SMA ,SMM-HC and S100protein). 2-To determine the expression of MMP2 expression in breast tissue and difference between normal ,benign ,non invasive breast lesion compared with invasive breast carcinoma by (ISH) Samples ,materials and methods: A total of 100 samples from breast tissue were included in this retro and prospective study. There were 10 histological samples of normal breast tissues as a control group and 90 samples contain benign and malignant breast lesions . The tissue samples were obtained from archival paraffin embedded blocks selected for the period from Jan. 2008 to June 2010 from the histopathology files of Al-Kadhimiya Teaching Hospital, Al-Yarmouk Hospital, Medical City Department of Teaching Laboratories, and from four private laboratories. For each case, 5 sections of 5µm thickness were taken; one representative section was stained with H&E and the second was stained immunohistochemically with smooth muscle actin(SMA) the third with smooth muscle myosin heavy chain (SMM-HC) and the fourth with S100 and the fifth was stained by in situ hybridization technique with MMP 2.The 30 case FNAC of palpable breast lesions were stained with SMA .The reactivity of each antibody was scored separately on the myoepithelium, myofibroblasts, vascular smooth muscle cells, and tumor (or benign epithelial) cells in each case. For each of the myoepithelial cell markers in each ductal carcinoma cases ,the intensity of immunoreactivity in MEC markers surrounding DCIS was compared with that of MEC surrounding benign ducts and lobular acini on the same slide . using light microscopy the degree of expressions(hybridization signals) in the cells of the examined tissue were determined in 10 fields under high power microscope (400X)in a semiquantitative fashion(as a percentage of positively stained cells) Results : All three antibodies were positive on the vast majority of myoepithelial cells in all cases except for SMMHC that expressed in 88% of cases only .No case showed S100 positive expression by myofibroblast or vascular smooth muscle cells while myofibroblast expressed positive staining in 82% and in 55%of cases for SMA and SMMHC respectively and vascular smmoth muscle cells expressed positive staining in 100%of cases for both SMA and SMMHC . although no tumor cells positive reaction was noted to SMA or SMMHC but in 64% of cases showed positivity for S100 protein . when we compared the intensity of staining for the MEC markers of DCIS cases with the staining intensity of MEC s surrounding normal ducts and lobules there was reduction of intensity and The most striking reduction in staining intensity was observed in SMMHC ;84%of DCIS cases showed reduced staining intensity for SMMHC in MEC surrounding the ducts compared with the normal MEC .Regarding S100 protein 72%showed reduction of DCIS associated MEC staining .in contrast ,staining intensity of DCIS –associated MEC for SMA was similar to that of normal MEC in all but 2 cases was with score 2 with slightly reduced compared to MEC surrounding normal ducts and lobules .no cases with negative (score 0 )in both SMA and S100 but in 3 cases with SMMHC (12%) There were no significant differences between high grade and non-high grade in situ ducal carcinoma in the proportion of cases showing reduced expression for any of MEC markers studied There were no significant differences in the immunohistochemical reduced expression of various antigens between invasive and non-invasive carcinoma . there was no significant differences in expression of MMP2 between benign and in situ (p value >0.05).But there was significant difference in MMP2 expression between benign and invasive and between in situ carcinoma and invasive (p value <0.05) Conclusions : 1.For the recognition of MECs the most sensitive markers are SMA,S100 followed by SMMHC which appear to be less sensitive . 2. All the three markers (SMA,S100 and SMMHC) are not specific for MECs because of cross reaction with other cells.
3. the sensitivity of these MEC markers is lower for DCIS-associated MECs than for MECs surrounding normal mammary ductallobular structures. This was most prominently noted for SMMHC but was also observed in a substantial minority of cases for S100 and. In contrast, the MEC marker that seem to be expressed in DCIS-associated MECs to a degree most similar to that seen in normal MECs are SMA .
4. MMP2 which is involve in stromal invasion is highly expressed in invasive carcinoma than in DCIS and it appear to be more expressed in stromal cells than in tumor cells .