Current concepts in diagnosis of unusual salivary gland tumors

Salivary gland tumors are relatively uncommon and account for approximately 3-6% of all neoplasms of the head and neck. Tumors mostly involve the major salivary glands, 42.9-90% of which occur in the parotid glands and 8-19.5% in the sub-mandibular glands; tumors in the sub-lingual glands being uncommon. Despite the plethora of different malignant salivary gland tumor presented to pathologists for diagnosis, there is consensus on a limited number of pathologic observations that determine treatment and outcome. There are few absolutes in salivary gland tumor diagnosis given the marked spectrum and overlap of differentiated cell types that participate in the numerous benign and malignant tumors. Thus, there are enumerating antibodies that may be helpful in resolving difficult differential diagnoses when applied with astute morphologic correlation. In general, immunohistochemistry as an ancillary diagnostic tool should be used sparingly and wisely as a morphologic adjunct because of the lack of specificity of many markers for specific histologic tumor types. The aim of this review is to discuss the molecular profiling of salivary gland neoplasms and correlate this with histogenesis of salivary gland neoplasms. We have elected to discuss and illustrate some of the unusual salivary gland tumors that the practicing pathologist find difficult to diagnose. These have been selected because they readily simulate each other but have very different clinical therapies and, therefore, should be included routinely in differential diagnosis.