[Immunohistochemical study of monomorphic adenoma (clear cell and basal cell) and pleomorphic adenoma of the parotid gland].

The present paper reports the results of an immunohistochemical study of 6 cases of monomorphic (2 clear cell, 4 basal cell) and 12 cases of pleomorphic adenomas in the parotid gland. The surgical specimens, embedded in paraffin, were tested by antisera vs. epithelial cell markers with epithelial membrane antigen (EMA) and cytokeratins (CK). They were also tested vs. myoepithelial and non-epithelial markers with S-100 protein and Glial Fibrillary Acidic Protein (GFAP). In pleomorphic adenomas, positive cells were found for all the tested antigens. Positive cell distribution showed a marked variability from case to case and even within each area, depending on cell morphology. In particular, areas showing tubular structures were constantly EMA-positive and CK-positive in more than 50% of the cases. In epithelioid areas EMA was negative while many cells were variably positive for CK, S-100 and GFAP. At times, the same cell proved positive to two different antigens. In those fuso-stellate (myxoid) cell areas considered to be of myoepithelial origin, cells were slightly CK-positive and widely GFAP and S-100 positive. In basal cell adenomas, widespread CK positivity was uniformly present while rare, focal positivity was evidenced for EMA and widespread non reactivity was found for S-100 and GFAP. In clear cell adenomas focal CK expression was found in the tubular lumina while clear cells, of myoepithelial origin, were steadily S-100 positive and GFAP-negative. It was noted that a sort of S-100/GFAP positive myoepithelial cell with fuso-stellate morphology was present in pleomorphic adenomas.(ABSTRACT TRUNCATED AT 250 WORDS)