Salivary Gland Carcinoma with DLG1::BRAF Gene Fusion: Report of a Case.

BACKGROUND

The widespread use of next-generation sequencing has allowed refinement of the classification and diagnosis of salivary gland neoplasms, leading to identification of recurrent gene fusions in a majority of salivary gland carcinoma types, and characterization of several novel entities. A small proportion of salivary gland carcinomas do not meet the diagnostic criteria for any known tumor type and are therefore classified as "salivary gland carcinoma, not otherwise specified". Given the ever-growing arsenal of tools to classify these lesions, the number of cases diagnosed as such is expected to continue decreasing.

CASE PRESENTATION: In this article we describe a novel DLG1::BRAF fusion in a high grade salivary gland carcinoma arising in the tongue of a 78 year-old woman. This tumor had solid and cribriform architectural features and was composed of a dual population of abluminal and mucinous cells. Immunohistochemically, it had variable SOX10 expression, variable and strong MUC4 reactivity and expression of p63 and p40 (delta Np63) in the abluminal cell population. The gene fusion retained the kinase domain of BRAF, without the self-inhibitory CR1 domain, which is expected to lead to upregulation of BRAF protein. The patient had a complete resection of her tumor, without evidence of local recurrence or metastasis 10 months after diagnosis.

CONCLUSION

These findings may represent a previously undescribed type of salivary gland tumor. However, additional reports of similar lesions are necessary for definitive characterization.