(403) Primary Synchronous Parotid Tumors - A Systematic Review

Introduction: While historically being associated with Warthin’s tumors, synchronous primary parotid tumors can occur across many histopathologic diagnoses and be either homogenous (same histology) or heterogeneous (different histology) in nature. This study focuses on determining the synchronous occurrence of parotid tumors and identifying the most prevalent combinations of tumor types.

Methods: A systematic review was conducted from 1965 to 2022. We identified observational studies from PubMed, EMBASE, SCOPUS, EBSCO, Cochrane Library, and Grey literature. The present study followed the PRISMA guidelines. Those studies describing parotid synchronous tumors were included. The primary outcome was to describe the frequency of the reported association.

Results: A total of 690 studies were identified and 25 studies met the inclusion criteria. From them, 19293 parotid patients were included. A total of 387 cases of primary parotid synchronous tumors were identified. The mean age was 61.3 (SD=7.7) years with M:F ratio of 2:1. Synchronous homogenous tumors were reported in 324 (83.7%) patients; synchronous heterogenous parotid tumors were reported in 63 (16.2%) patients. Among the homogenous synchronous tumors, Warthin tumor is the most commonly reported tumor in 307/324 (94.7%) cases, followed by pleomorphic adenoma in 9/324 (2.7%) cases. The commonest heterogeneous primary parotid tumor combinations include Warthin tumor with pleomorphic adenoma in 32/63 (50.7%) cases, followed by Warthin and acinic cell carcinoma in 5/63 (7.9%) cases. Unilateral and bilateral synchronous tumors are found in 65.8% and 34.2% of cases respectively. Overall, primary synchronous parotid tumors occur at the rate of 12 out of 100 parotid tumor cases, with homogenous and heterogenous tumors occurring at 10 out of 100 and 2 out of 100 parotid tumor cases, respectively.

Conclusions: This is the most extensive study to determine the rate of synchronicity of parotid tumors. The occurrence of specific subtypes of parotid tumors which simultaneously may help surgeons with clinical/surgical decision-making with respect to this patient population.