[1234] WT-1 Expression in Salivary Gland Pleomorphic Adenomas: A Reliable Marker of Neoplastic Myoepithelium

G Langman, CL Andrews, A Weissferdt. Birmingham Heartlands Hospital, Birmingham, West Midlands, United Kingdom; MD Anderson Cancer Center, Houston, TX

Background: Pleomorphic adenoma is a benign salivary gland neoplasm with a diverse morphology. This is thought to be a function of the neoplastic myoepithelial cell which shows histological and immunophenotypical variability. Wilms' tumor 1 gene (WT-1) protein, involved in bi-directional mesenchymal-epithelial transition, has been detected by reverse transcription polymerase chain reaction in salivary gland tumors showing myoepithelial-epithelial differentiation. The aim of this study was to investigate the immunoreactivity of WT-1 in pleomorphic adenomas and compare the pattern of staining with p63 and calponin, two reliable markers of myoepithelial cells.
Design: Thirty one cases of pleomorphic adenoma were selected, 28 of which included normal salivary gland tissue. The myoepithelium was classified as either myoepithelial-like (juxtatubular and spindled), modified myoepithelium (myxoid, chondroid and hyaline) and transformed myoepithelium (solid epithelioid, squamous and basaloid-cribriform). Immunohistochemistry for WT-1, p63 and calponin was assessed semi-quantatively in each myoepithelial component as well as non neoplastic myoepithelial cells and inner tubular epithelial cells.
Results: There was no immunostaining of the tubular epithelial cells by any of the markers. In contrast to p63 and calponin, WT-1 did not react with normal myoepithelial cells. Cytoplasmic WT-1 staining was present in all pleomorphic adenomas and in 30 cases (97%) more than 50% of neoplastic myoepithelial cells were highlighted. p63 and calponin stained the myoepithelium in 30 tumours. In comparison, however, 50% of the cells were positive in 22 (71%) and 12 (39%) cases respectively. Staining with WT-1 showed less variability across the spectrum of myoepithelial differentiation. The difference was most marked in the transformed myoepithelium where the solid epithelioid and basaloid/cribriform growth patterns showed strong and uniform expression with WT-1.
Conclusions: WT-1 is a sensitive marker of the neoplastic myoepithelial cell in pleomorphic adenomas. The role of this protein in influencing the mesenchymal-epithelial state of cells suggests WT-1 and the myoepithelial cell has an important role in the histogenesis of pleomorphic adenomas. The staining of WT-1 in other salivary gland tumours and its potential use in diagnostic surgical pathology requires further study.
Category: Head & Neck

Tuesday, March 23, 2010 11:00 AM

Platform Session: Section G, Tuesday Morning

 

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