Multiple reciprocal translocations in salivary gland mucoepidermoid carcinomas

Mucoepidermoid carcinoma, the most common human malignant salivary gland tumor, can arise from both major and minor salivary glands, including sites within the pulmonary tracheobronchial tree. We performed comparative genomic hybridization (CGH) and spectral karyotyping (SKY) on two tumor cell lines: H3118, derived from tumor originating in the parotid gland, and H292, from tumor in the lung. In both cell lines, CGH showed a partial gain within the short arm of chromosome 7 and SKY revealed the presence of the previously reported reciprocal translocation t(11;19)(q21;p12). Additional chromosomal rearrangements were found in both cell lines, including three more reciprocal translocations in cell line H292 [t(1;16), t(6;8)x2] and three other reciprocal translocations in cell line H3118 [t(1;7), t(3;15), and t(7;15)]. A review of the literature of other reported cases of mucoepidermoid carcinomas analyzed with standard G-banding techniques, as well as distinct benign salivary gland tumors, such as pleomorphic adenomas and Warthin tumor, confirmed the presence of a karyotype dominated by reciprocal translocations. Four chromosomal bands were involved in chromosomal translocations in both cell lines: 1q32, 5p15, 7q22, and 15q22. Fluorescence in situ hybridization studies showed that the breakpoints in these four bands were often within a few megabases of each other. The involvement of similar chromosomal bands in breakpoints in these two cell lines suggests that these regions may be predisposed or selected for chromosomal rearrangements in this tumor type. The presence of multiple reciprocal translocations in both benign and malignant salivary gland tumors may also suggest a particular mechanism within mucous or serous glands mediating chromosomal rearrangements.