A rare case of bilateral multifocal nodular oncocytic hyperplasia of the parotid gland

Multifocal nodular oncocytic hyperplasia (MNOH) is an extremely rare pathological entity occurring in the parotid gland, even more rarely described in the submandibular gland. We report a case of bilateral parotid MNOH in a 71-year-old woman and perform a search of the existing literature that is compiled in a table. Fifty-nine cases are described in 34 publications. Half of the published cases presented as bilateral lesions, either synchronous or metachronous. Other lesions of the oncocyte-spectrum such as oncocytomas are frequently described on the ground of oncocytic hyperplasia. MNOH rarely occurs before the age of 40 years and mean age of the described cases is 62 years. The condition is considered as benign by all authors, but surgery was performed in nearly all cases, most often due to a lack of diagnostic certainty. Nevertheless, the radiologic presentation of MNOH is often highly suggestive. Based on the existing literature, recommendations for the management of MNOH are formulated.