Expression of CD44s, CD44v3 and CD44v6 in benign and malignant breast lesions: correlation and colocalization with hyaluronan

Aims: To examine the expression of CD44s, CD44v3 and CD44v6 in breast lesions, and to correlate it with the expression of hyaluronan (HA). Methods and results: CD44 expression was studied in 75 breast tissue samples, consisting of benign, premalignant and malignant breast lesions, using immunohistochemistry. CD44s, but not CD44v3 or CD44v6, was found in the stromal cells, and it was similar in benign and malignant tumours. In benign lesions CD44v6 was detected in 20-30% of the ductal epithelial cells, while CD44v3 and CD44s were not expressed. CD44s, CD44v3 and CD44v6 were all up-regulated in the in situ carcinomas and invasive carcinomas. The level of CD44 expression in carcinoma cells did not correlate with the type or differentiation of the tumours. CD44 and HA expression levels were not closely linked in the benign or malignant breast lesions, because HA was overexpressed later in breast cancer progression than CD44. However, in breast carcinomas CD44 and HA positivity was often found in the same areas of the sections, and the dual staining confirmed actual colocalization of CD44s and HA in the same cells. Conclusions: CD44s, CD44v3 and CD44v6 are up-regulated earlier than HA in breast carcinoma progression, and in later stages they often colocalize with cell surface HA.