How should a 9‑mm asymptomatic left parotid gland lesion be managed, including evaluation of cervical lymph nodes, when pleomorphic adenoma cannot be excluded?

Management of a 9-mm Asymptomatic Left Parotid Lesion with Possible Pleomorphic Adenoma

For a 9-mm asymptomatic parotid lesion where pleomorphic adenoma cannot be excluded, obtain ultrasound as first-line imaging followed by fine needle aspiration biopsy (FNAB) with Milan System reporting to establish diagnosis, then proceed with partial superficial parotidectomy with facial nerve preservation if pleomorphic adenoma is confirmed. 1, 2

Initial Diagnostic Workup

Imaging Strategy

• Ultrasound is the first-line imaging modality for this parotid lesion, as it effectively differentiates intraparotid from extraparotid masses, identifies features suspicious for malignancy, and can guide FNAB if needed 2
• Ultrasound distinguishes solid from cystic lesions and evaluates vascular characteristics through color-flow Doppler 2
• If concerning features emerge or the lesion increases in size, proceed to MRI with and without IV contrast for comprehensive evaluation of tumor extent, deep lobe involvement, local invasion, and relationship to the facial nerve 2, 1

Tissue Diagnosis

• FNAB with risk of malignancy (ROM) reporting using the Milan System for Reporting Salivary Gland Cytopathology is recommended for preoperative evaluation 1
• Consider ancillary testing (immunohistochemistry or molecular studies) on FNAB specimens to support diagnosis 1
• Be aware that pleomorphic adenomas with mucinous and squamous metaplasia can mimic mucoepidermoid carcinoma on FNA, making adequate tissue sampling critical 3
• Intraoperative frozen section has 98.5% sensitivity and 99% specificity for detecting malignant parotid tumors, but should not be the sole basis for major decisions like facial nerve sacrifice 1, 4

Cervical Lymph Node Evaluation

• Evaluate for associated lymphadenopathy which may indicate a malignant process 2
• For this small (9-mm) lesion suspicious for pleomorphic adenoma, lymph node involvement would be extremely unusual, as pleomorphic adenomas are benign neoplasms 5, 6
• If lymphadenopathy is present, this should raise concern for malignancy rather than pleomorphic adenoma 2

Surgical Management

Definitive Treatment Approach

• Partial superficial parotidectomy with facial nerve preservation is the appropriate surgical approach for confirmed pleomorphic adenoma of this size 1, 4
• Complete excision of the tumor is the definitive treatment, as enucleation results in higher recurrence rates 5
• The facial nerve must be preserved when preoperative function is intact and a dissection plane can be created between tumor and nerve 1, 4, 5

Surgical Extent Considerations

• For benign tumors like pleomorphic adenoma, partial superficial parotidectomy is sufficient and can be safely performed as an outpatient procedure 1
• Additional excision of uninvolved parotid parenchyma is not necessary for benign lesions 4, 1
• Partial superficial parotidectomy removes the tumor with a greater cuff of healthy parotid tissue than extracapsular dissection, minimizing recurrence while limiting complications such as facial nerve dysfunction and Frey syndrome 7

Expected Outcomes

• Superficial or total parotidectomy with facial nerve preservation results in local control rates of 95% or higher for pleomorphic adenoma 8
• The main surgical complication is 7th nerve injury, which should be minimized through meticulous technique 8

Common Pitfalls to Avoid

• Do not perform simple enucleation, as this leads to higher recurrence rates due to incomplete capsular removal 5, 7
• Do not sacrifice the facial nerve based on indeterminate preoperative or intraoperative results alone—major harm should be avoided without definitive evidence of malignancy 4, 1
• Do not rely solely on FNA cytology when features suggest mucinous or squamous metaplasia, as this can mimic mucoepidermoid carcinoma and lead to overtreatment 3
• Pleomorphic adenomas can grow to extensive sizes if left untreated, so timely diagnosis and treatment are essential 5

Natural History Considerations

• Pleomorphic adenomas progress slowly and present as asymptomatic swellings, typically in middle-aged women 6, 8
• Left untreated, they can produce significant morbidity and, rarely, death 8
• While "continued follow-up" may seem conservative, definitive surgical excision is the standard of care once pleomorphic adenoma is diagnosed, given the excellent outcomes with surgery and the risk of progressive growth 5, 8