The significance of the margin in parotid surgery for pleomorphic adenoma

Superficial parotidectomy dramatically reduced the high rates of tumor recurrence that occurred with simple enucleation of parotid pleomorphic adenoma (PPA). However, there is not agreement in the medical literature confirming the exact margin of parotid tissue to be resected to avoid recurrence. Worldwide, SP and/or partial superficial parotidectomy (PSP) is commonly practiced for the treatment of PPA. In Europe and Asia, reports covering a spectrum from total parotidectomy (TP) to extracapsular dissection (ECD) are common. The outcomes (capsular exposure, tumor-facial nerve interface, capsular rupture, recurrence, facial nerve dysfunction, and Frey syndrome) from surgical treatment of mobile, superficial PPA smaller than 4 cm are not significantly altered by surgical approach (TP, PSP, or ECD).

Retrospective series of pathological specimens were correlated with their clinical outcomes to compare TP, PSP, and ECD. Historical data review and meta-analysis were also performed.

Matched pairs of 60 pathological specimens of PPA (20 cases treated by TP, PSP, and ECD, respectively) were compared for capsular exposure and the degree of cellularity of tumors. Statistical analysis of the respective rates of tumor-facial nerve interface, capsular rupture, recurrence, permanent and transient facial nerve dysfunction, and Frey syndrome was performed.

Focal capsular exposure occurs in virtually all parotid surgery for PPA, regardless of the type of operation (margin). Dissecting PPA from the facial nerve led to a positive margin in 25% of cases. Capsular rupture does result in a significantly higher rate of recurrence and did not vary among surgical approaches (TP, PSP, and ECD). Tumor-facial nerve interface did not vary significantly by surgical approach. A less complete parotidectomy did not result in a higher rate of recurrence. Less parotid tissue sacrifice did not result in a lower rate of permanent facial nerve dysfunction, although it did result in significantly less transient facial nerve dysfunction and Frey syndrome. Hypocellular tumors did not have a higher incidence of capsular rupture or recurrence. Multicentric PPA was not identified in the clinically negative deep lobe for TP specimens. The most common cause of recurrence for PPA today is enucleation.

The major outcomes of surgical treatment for small PPA (capsular exposure, tumor-facial nerve interface, capsular rupture, recurrence, and permanent facial nerve dysfunction) are not significantly altered by the amount of parotid tissue sacrifice (TP, PSP, or ECD). More complete parotidectomy results in higher rates of transient facial nerve dysfunction and Frey syndrome. Focal capsular exposure occurs in virtually all cases of parotid surgery for PPA. Dissecting PPA from the facial nerve results in cases with positive margins because of incomplete capsule or perforating pseudopodia. Few separations of pseudopodia from the main tumor occur with expertly performed contemporary parotid surgery because most of the PPA has a margin of normal parotid tissue. Minimal margin surgery in ECD is not recommended.