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Purpose

Superficial parotidectomy (SP) with facial nerve dissection dramatically reduced the high rates of tumor recurrence that occurred with simple enucleation of parotid pleomorphic adenoma (PPA) in the second half of the 20th century. However, there is no agreement in the current medical literature confirming the exact margin of parotid tissue to be resected to avoid recurrence and reduce morbidity. Partial capsule exposure is near-universal even with total parotidectomy where the tumor abuts the facial nerve. More complete parotidectomy results in higher rates of transient facial nerve dysfunction and Frey syndrome . A better understanding of histopathology, the use of magnification, bipolar coagulation to control hemostasis, and nerve integrity monitoring have led to less invasive surgery for PPA. Partial SP (PSP) with facial nerve dissection and a 2-cm margin of normal parotid parenchyma, except where the tumor abuts the facial nerve, is the generally favored approach to small (<3 cm) benign tail of PPA, reducing morbidity without increasing recurrence. Extracapsular dissection (ECD) dissects a small cuff of normal parotid parenchyma around the tumor without facial nerve dissection. Selected reports on ECD, mostly from Europe but also from North America, suggest equivalent results for recurrence and better results for morbidity. The minimally invasive low-impact surgery of ECD presents a potentially attractive surgical option. Because the facial nerve is not controlled from the outset and there is a risk of rupture of the tumor, ECD is a procedure for experienced surgeons. This study attempts to answer the following hypothesis: the margin of normal parotid tissue surrounding a PPA is less for ECD compared with PSP.

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Materials and methods

Institutional review board approval was obtained for this study. Twelve consecutive parotidectomy procedures with a final pathology report of PPA were retrospectively measured for margin (the percent of capsule exposure around the tumor) ( Table ). The lead author learned the surgical technique and indications for ECD as a first assistant with high-volume salivary gland surgeons in England and Germany as well as through the study of publications. Twelve patients met the potential criteria for ECD with preoperative imaging and preoperative fine-needle aspiration cytology consistent with benign neoplasm. The study period included cases from 2009 to 2010 (20 months). The 12 patients all had preoperative favorable clinical characteristics including mobile, tail of parotid, and superficial tumors that were less than 3 cm. In 8 of these highly selected patients, ECD with nerve integrity monitoring and loop magnification was performed. Four parotid surgical procedures intraoperatively not meeting all criteria underwent PSP and served as controls. The only criterion that was not met in the 4 patients who underwent PSP rather than ECD was poorly palpated tumor capsule intraoperatively. All patients had frozen-section analysis. All 12 patients had a frozen-section analysis consistent with PPA or benign neoplasm without malignant features. The 12 consecutive selected parotidectomy procedures in this retrospective study had a final pathology report of PPA. They were measured for margin (the percent of capsule exposure around the tumor). The pathologist was blinded for operation type when measuring margin.

All cases were processed in a similar manner. The entire intact specimen was inked before serial sectioning. Each salivary gland and contained tumor mass was sectioned at 2- to 3-mm intervals. In all cases, the entire tumor mass was submitted for histologic examination. Blocks were processed for routine hematoxylin and eosin–stained sections. Diagnosis was rendered by 1 or more of 8 pathologists, often with intradepartmental review and concurrence.

The percent capsular exposure was calculated as follows: on every hematoxylin-and-eosin glass slide containing tumor, the perimeter of the entire tumor mass was measured in millimeters. The overall tumor perimeter was expressed as the sum of distance on all glass slides. In addition, the perimeter of the exposed tumor (defined as pleomorphic adenoma adjacent to the ink with no intervening nonneoplastic salivary gland) was also measured in millimeters. Again, the perimeter of capsular exposure was expressed as the sum of distance on all glass slides. The percent capsular exposure is the ratio of capsular exposure (in millimeters) to the entire tumor perimeter (in millimeters). Because every tumor was entirely submitted for microscopic examination and all were sectioned at 2- to 3-mm intervals, it was concluded that the distances in millimeters were representative of the overall surface area; for example, a tumor perimeter of 205 mm and a capsular exposure of 150 mm results in a 73% capsular exposure.