Pediatric Epithelial Salivary Gland Tumors: Spectrum of Histologies and Cytogenetics at a Children's Hospital

There are conflicting reports regarding the relative frequency of benign and malignant epithelial salivary gland tumors in children. There are only a few reports of the cytogenetic abnormalities in the pleomorphic adenomas (PA) that arise in children, and even less information regarding the pleomorphic adenoma gene 1 (PLAG1) and high motility group A2 (HMGA2) histochemical staining in PAs, or their correlation with histologic types (stromal vs epithelial predominance). A retrospective 14 year review of epithelial salivary gland tumors encountered at a children's hospital identified 13 tumors: 12 PAs and 1 acinic cell carcinoma (ACC). No mucoepidermoid carcinomas were identified. Tumors arose in the parotid (7) and other sites (2 submandibular, 4 minor). Ten PAs in our cohort had cytogenetic studies. Four were normal, 5 involved 8q12, and 1 involved 12q13. Immunohistochemistry identified an additional 2 PAs with PLAG1 staining, and 5 additional PAs with HMGA2 staining. One tumor with ins(18;8)(q21.1;q12q22.2) had no PLAG1 staining, but stained with HMGA2. This ins(18;8) may not have involved the PLAG1 gene. There was no demonstrable correlation of 8q12/PLAG1 staining or 12q13/HMGA2 staining with histologic type. Thus we found abnormalities in either 8q12/PLAG1 staining or 12q13/HMGA2 staining in all PAs. The HMGA2 staining in 50% of PAs suggests that it may be more frequently involved in PAs than previously thought based on cytogenetic studies, at least in children.