Salivary gland tumors are a morphologically and clinically diverse group of neoplasms which may present significant diagnostic and management challenges. Cell adhesion molecules (CAMs) are glyco-proteins that are present on the external surface of the cell membrane. CD44 is a cell adhesion molecule belonging to systemic IgCAMs family, and is remarkable for its ability to generate alternatively spliced forms, many of which differ in their activities. This remarkable flexibility has led to speculation that CD44, via its changing nature, plays a role in some of the methods that tumor cells use to progress successfully through growth and metastasis.
Aim of the work: To investigate the expression of CD44v6 in different types of salivary glands tumors and to correlate the results with some established prognostic factors. Materials and methods: Sixty cases were studied. 21 were pleomorphic adenomas, 9 Warthins tumors, 6 monomorphic adenomas, 9 mucoepidermoid carcinomas, five adenoid cystic carcinomas, in addition to10 normal controls. Clinical data were obtained from the referring clinical departments. The biopsy specimens were obtained by excision, true cut needle biopsy, or punch biopsy. Cases were selected by reviewing the hematoxylin and eosin (H&E) stained slides. Immunohistochemistry was done using the CD44v6 mouse monoclonal antibody raised against human species. Results: CD44v6 was +ve in 46/60 (76.7%) of salivary gland tumors studied; 35/40 (87.5%) benign salivary glands tumors and 11/20 (55%) malignant salivary gland tumors and this difference was statistically significant (P < 0.01). CD44v6 was +ve in 16/21 (76%) of pleomorphic adenoma, in 9/9 (100%) of Warthin's tumors and in 6/6 of monomorphic adenoma. CD44v6 was +ve in 5/ 9 of mucoepidermoid carcinoma; 4/5 (80%) of low and intermediate grade mucoepidermoid carcinoma and in 1/4 (25%) of high grade malignant mucoepidermoid carcinoma. The 4 studied high grade malignant mucoepidermoid carcinoma were lymph node metastasis +ve. CD44V6 was +ve in 4/5 (80%) of adenoid cystic carcinoma. There was a statistically significant decrease in CD44v6 positivity (P < 0.03) in high grade malignant salivary gland tumors compared to low and intermediate grade tumors. There was also a statistically significant decrease in CD44v6 positivity (P < 0.01) in malignant salivary gland tumors received with lymph node metastasis compared with those lymph node metastasis negative cases.
Conclusion: 1- Down regulation of CD44v6 plays an important role in malignant transformation of salivary gland tumors. 2- The degree of down-regulation is correlated with progression towards higher grades and also with lymph node metastasis