Pleomorphic Adenoma of the Parotid Gland and the Parapharyngeal Space: Two Diametrically Opposing Surgical Philosophies for the Same Histopathologic Entity?

Abstract

Background: The aim of this study was to investigate the histopathologic findings in parotid and parapharyngeal pleomorphic adenomas and draw conclusions concerning the surgical strategy. Methods: Retrospective study of medical charts of patients with resected pleomorphic adenomas (PA) between 2005 and 2020 at two tertiary medical referral centers. Histologic specimens were reexamined by an experienced head and neck pathologist. Patients with insufficient/incomplete data were excluded from our study sample. Results: A total of 844 patients formed our study sample (291 men, 553 women, average age 48.9 years); 786 cases had a PA in the parotid gland (PG) (93.1%), and the remaining 58 cases had a PA in the parapharyngeal space (PS) (6.9%). Recurrences were detected in 8/844 cases (7/786 in the PG, 1/58 in the PS, 0.94% in total) with a mean follow-up time of 86.7 months (10–189 months) with no statistically significant differences between the study groups (p = 0.527). Our analysis showed that parapharyngeal pleomorphic adenomas are characterized by a lower incidence of an intact anatomical capsule (71.4% vs. 82.6%, p = 0.035) and a remarkably more frequent occurrence of satellite nodules (20.7% vs. 7.5%, p < 0.001). Conclusions: The more challenging histopathologic profile of parapharyngeal pleomorphic adenomas points towards the fact that parapharyngeal surgery should remain in the hands of experienced surgeons at high-volume centers.

Treatment of Salivary Gland Diseases: Established Knowledge, Current Challenges and New Insights

“…With respect to pleomorphic adenomas of the parotid gland, understanding the histological characteristics of the tumour capsule and the potential clinical relevance of their biological behaviour is fundamental for the management of these entities. Undoubtedly, the different histological subtypes, the various degrees of capsular intactness and the formation of pseudopodia, as well as satellite nodules, constitute a demanding profile with apparent clinical-surgical implications [1]. Historically, the surgical management of pleomorphic adenomas has followed a sinusoidal course from "enucleation" (dissection along the capsule or even opening the capsule and removing tumour material) in the 1940s (with recurrence rates of up to 45%) to standardised facial nerve dissection after the 1950s (with a high risk of iatrogenic injury of the facial nerve), resulting in a minimum of extracapsular dissection by the end of the last century.…”