Background: The interaction between transmembrane receptors on epithelial tumor cells and the surrounding extracellular matrix molecules is important in tumor progression and metastasis. This interaction is best exemplified by the relationship of the receptor CD44 and the extracellular matrix component hyaluronan (HA). This study seeks to evaluate the expression and the correlation of CD44s, CD44v6, and HA in normal, hyperplastic, and malignant breast epithelium and stroma.
Materials and methods: Archival paraffin-embedded tissue from cases of normal breast tissue (n=10), intraductal hyperplasia without atypia (n=13), ductal carcinoma in situ (DCIS) (n=24), stage I infiltrating ductal carcinoma (n=28), stage II infiltrating ductal carcinoma (n=31), and their corresponding positive lymph nodes were retrieved from the surgical pathology files. Tissue sections were evaluated for the expression of CD44s, CD44v6, and HA in the epithelial and stromal cells by immunohistochemistry.
Results: Ductal epithelial cells and myoepithelial cells expressed CD44s in all cases of normal and benign breast tissue. The expression of CD44s in breast epithelium progressively decreased with increasing deviation from normal histology: 83% in DCIS, 46% in stage I ductal carcinoma and 26% in stage II ductal carcinoma. The reverse trend was observed for CD44v6 in ductal epithelium: 0% in normal breast, 15% in intraductal hyperplasia, 100% in DCIS, 82% in stage I infiltrating ductal carcinoma, 94% in stage II carcinoma, and 100% of metastatic carcinoma in the lymph nodes. HA was noted exclusively in the stroma but not in the epithelial cells. HA was faintly expressed in the intralobular stroma of normal breast tissue, confined to a narrow faint band adjacent to intraductal hyperplasia and localized to a broad well-defined band around DCIS. Stromal HA staining was more diffuse and intense in infiltrating carcinomas and was particularly pronounced surrounding the metastatic deposits in lymph nodes.
Conclusions: This study demonstrates decreased expression of CD44s accompanied by increased expression of CD44v6 and increased stromal HA in breast cancer. These findings suggest that CD44s, CD44v6, and HA play complementary roles in the development and progression of breast cancer.