Epithelial-myoepithelial carcinoma of the parotid gland-evidence of contrasting DNA patterns in two different histological parts.

Epithelial-myoepithelial carcinoma (EMC) is a rare neoplasm arising predominantly in the salivary glands, in particular in the parotid gland. We report the morphological features of an epithelial-myoepithelial carcinoma of the parotid gland with one lymph-node metastasis including a molecular genetic study of this tumor. Immunohistochemical and ultrastructural results confirmed the epithelial-myoepithelial dualism of the carcinoma. The loss of heterozygosity (LOH) analysis revealed different LOH results for the solid and the tubular growth pattern of the primary tumor, but showed identical findings for the solid primary tumor component and the lymph node metastasis which had also a solid appearance. LOH could be demonstrated in the whole primary tumor at D13S217 (13q12) and D18S58 (18q21). In three other microsatellite loci [D9S162 (9p22-p21), D10S251 and D10S541 (surrounding the PTEN/MMAC1 gene on 10q23-q24)], clearly recognizable LOH was found in the solid part and in the metastasis, whereas the tubular component demonstrated only a slight decrease of the same allele. No mutation or methylation of the p16 gene or alteration of the PTEN/MMAC1 gene could be found. Nevertheless, our results provoke a discussion, whether these genetic alterations could be considered as determinants of histologically and prognostically divergent types in EMC.