Approach to a parotid mass: from diagnosis to surgery

Key points

• Most parotid masses are benign (most commonly pleomorphic adenoma and Warthin tumour), but pain, rapid growth, facial nerve weakness, fixation or skin involvement raise the suspicion of malignancy.
• The first step is usually ultrasound-guided fine-needle aspiration (FNA); the result should be reported in a risk-based way using the Milan System for Reporting Salivary Gland Cytopathology.
• MRI stands out for assessing deep lobe and parapharyngeal extension and perineural spread; CT is preferred when bone involvement is suspected.
• ASCO 2021 recommends preserving a functioning facial nerve when a plane can be developed between the tumour and the nerve, and advises that decisions with major consequences such as facial nerve resection should not rest on indeterminate preoperative or intraoperative diagnoses.
• Elective neck treatment is recommended for the clinically N0 neck in high-grade and T3–T4 tumours; indications for adjuvant radiotherapy are based on specific histopathological features.

History and examination

The duration of the mass, growth rate, pain, previously excised skin lesions (especially on the scalp, ear and face) and radiation history should be asked about. In populations with heavy sun exposure, metastatic cutaneous squamous cell carcinoma to parotid lymph nodes is an important differential diagnosis, so the head and neck skin is examined carefully.

Each branch of the facial nerve should be assessed separately and preoperative function documented (e.g. House–Brackmann). On oropharyngeal examination, medial displacement of the tonsil suggests deep lobe or parapharyngeal extension. The cervical lymph nodes and trismus are also assessed.

Imaging and tissue diagnosis

Surgical options

• Extracapsular dissection: used for selected small, mobile, superficial benign tumours. A meta-analysis reported similar recurrence and lower transient facial paresis compared with superficial parotidectomy; however, the data are largely retrospective and patient selection is decisive.
• Partial superficial parotidectomy: removal of the tumour with a cuff of normal tissue after identification of the facial nerve trunk and relevant branches; ASCO also considers it an option for appropriately located superficial T1–T2 low-grade cancers.
• Superficial, subtotal or total parotidectomy: because of the risk of intraparotid nodal metastasis, at least a superficial parotidectomy, with consideration of total or subtotal parotidectomy, is recommended for high-grade or T3–T4 parotid cancers; deep lobe tumours also usually require a wider resection.
• In pleomorphic adenoma, capsular rupture and enucleation increase the risk of recurrence; carcinoma ex pleomorphic adenoma may develop in tumours left untreated for a long time.

Intraoperative facial nerve monitoring is widely used and may help locate the nerve, but it does not replace anatomical identification and careful dissection. Frozen section may support decisions on extent of resection and neck dissection, but because of histological diversity it is limited in determining the exact tumour type. Irreversible decisions such as sacrificing the facial nerve should therefore not be based on an indeterminate frozen section result alone.

ASCO 2021 recommendations for malignant tumours

• Facial nerve: a nerve with intact preoperative function and a dissectable plane from the tumour should be preserved; if there is preoperative weakness, or branches are encased or grossly involved by confirmed malignancy, the involved branches should be resected.
• Elective neck: elective neck treatment rather than observation is recommended for the clinically N0 neck in T3–T4 and high-grade tumours; for parotid cancers, ipsilateral selective dissection may generally include levels II–IV. In a cN1 neck, involved and at-risk levels are dissected, extended to adjacent levels where needed.
• Postoperative radiotherapy: recommended for all resected adenoid cystic carcinomas and in the presence of high grade, positive surgical margins, perineural invasion, lymph node metastasis, lymphatic or vascular invasion, or a T3–T4 tumour; it may be considered for close margins or intermediate-grade tumours. Radiotherapy is recommended to start within 8 weeks of surgery.
• Systemic therapy: routinely adding concurrent chemotherapy to adjuvant radiotherapy outside a clinical trial is not recommended. In recurrent or metastatic disease, testing for targetable alterations such as AR, HER2 and NTRK guides treatment selection.

Complications and patient counselling

• Facial nerve weakness: temporary weakness is considerably more common than permanent weakness and usually recovers within weeks to months; the risk of permanent weakness rises with tumour location, size and extent of surgery.
• Frey syndrome (gustatory sweating): sweating and flushing over the parotid region during meals; its frequency varies with the extent of surgery, and options such as botulinum toxin can be used in symptomatic cases.
• Great auricular nerve involvement: numbness of the earlobe and surrounding area is common and decreases over time in most patients.
• Sialocele or salivary fistula, haematoma, infection and contour defect are other possible problems; most are managed conservatively.

Implications for clinical practice

• Preoperative ultrasound-guided FNA with a report that includes the Milan category provides a common language for the extent of surgery and patient counselling.
• When deep lobe extension, facial nerve weakness or perineural spread is suspected, MRI should be completed before surgical planning.
• Malignant tumours should be reviewed by a multidisciplinary tumour board regarding adjuvant treatment and neck management.
• The approaches described are a general framework; the type and extent of surgery are tailored to each patient according to examination, imaging and cytology results.

Limitations and currency note

Many ASCO recommendations rest on intermediate or low-quality evidence and expert consensus; the full text of the guideline should be consulted for evidence levels and recommendation strengths. Risks of malignancy in the Milan system may vary between centres. AJCC has published a Version 9 protocol for minor salivary gland cancers, effective in 2026; check which staging version you use. Because guidelines are updated regularly, readers should consult the current version; this text is not an individual treatment recommendation.