Are Multiple Tumors of the Parotid Gland Uncommon or Underestimated?

Parotid gland tumors are mostly solitary tumors of the salivary gland tissue. There is limited evidence about multifocal tumor growth of the parotid gland.

We reviewed medical records of 796 consecutive parotidectomies in 758 patients over the last 40 years in our department, and investigated the incidence and histological type of synchronous and metachronous parotid tumors. Multifocal recurrent tumors and hybrid tumors were excluded.

We identified 93 (13%) patients with multiple parotid lesions. Their mean age was 63 (range=15-93) years. Multiple parotid tumors were found unilaterally in 59% and bilaterally in 41% of cases. The contralateral tumor was diagnosed synchronously in 13 of 38 (34%) cases and in 25 of 38 (66%) cases metachronously. The time separating the diagnoses of both contralateral tumors ranged between one and eleven years. The same histological type was found in 95% of the tumors, and 96% of the parotid tumors had lymphatic origin. Warthin tumors (65%) were the most frequent histological type.

Every sixth patient with a parotid tumor has multifocal tumor lesions. The majority of multifocal parotid tumors have a lymphoid element, while multifocal growth is uncommon in other histological types.