Cytogenetic similarities between two types of salivary gland carcinomas: adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma

Adenoid cystic carcinoma (ACC) and polymorphous low-grade adenocarcinoma (PLGA) are low-grade adenocarcinomas of salivary glands with a putative common histogenesis from the intercalated ducts but featuring distinct histological appearances. Hybrid tumors containing areas with histological patterns of both neoplasms have been reported but, to our knowledge, the question of their genotypic similarity has not yet been approached. As part of an ongoing study on cytogenetic characterization of salivary gland tumors, from a group of 24 malignant neoplasms, three out of five cases of ACC and three of four cases of PLGA were selected for their similar karyotypic changes. All of them displayed chromosome 12 abnormalities, affecting the 12q12–q13 region in four (all ACC cases and one PLGA case), 12q22 in one PLGA case, and 12p12.3 in the remaining. From this group of neoplasms, one PLGA and one ACC showed the same t(6;12)(p21;q13). Our findings favor the concept that tumors of salivary glands displaying epithelial and myoepithelial phenotypes share a common histogenesis.