Salivary gland carcinosarcoma: immunohistochemical, molecular genetic and electron microscopic findings

Salivary gland carcinosarcoma. or true malignant mixed tumor, is a very rar e and extremely aggressive neoplasm. The clonality and clonal origin of thi s tumor are discussed controversially. We report a carcinsarcoma of the lef t parotid gland in a patient who subsequently died of cutaneous, lymphatic and pulmonary metastases. Immunohistochemical staining, electron micrograph analysis, loss of heterozygosity (LOH) analysis and sequence analysis were performed on this tumor sith an adenocarcinomatous and a predominant spind le cell-like component. While smooth muscle actin was undetectable by immun ohistochemistry. cytoplasmatic myoepithelial structures could be detected b y electron microscopy. LOH analysis at 12 genomic locations detected comple te deletion of one allele at 17p13.1. 17q21.3, and 18q21.3 indicating allel ic loss in both components of the tumor. Double strand sequencing of the re maining allele of the p53 tumor suppressor gene revealed a wild-type allele . Based on our results, we favor the hypothesis of monoclonal origin of thi s salivary gland carcinosarcoma with a common stem cell that could be the m yoepithelial cell and an inactivated tumor suppressor gene on chromosome 17 other than p53. (C) 2000 Elsevier Science Ltd. All rights reserved.