What is the appropriate workup and treatment for a patient presenting with a parotid gland mass?

Parotid Gland Mass Workup

Order MRI with and without IV contrast as the preferred initial imaging modality, followed by ultrasound-guided fine needle aspiration biopsy (FNAB) to establish tissue diagnosis before proceeding to surgical management. 1

Initial Clinical Assessment

Immediately evaluate for these critical red flags that suggest malignancy or serious complications:

• Facial nerve function: Any facial weakness or palsy indicates either malignancy or serious complication requiring emergency evaluation 2
• Pain characteristics: Painful swelling typically suggests infection or inflammation, while painless masses raise concern for malignancy 2
• Mass characteristics: Hard, fixed, and large masses (>3 cm) are more often malignant compared to mobile, soft masses 3
• Associated symptoms: Difficulty swallowing, trismus, or regional dysesthesia indicate deep lobe involvement or perineural spread 1
• Lymphadenopathy: Palpable neck nodes require immediate attention, as intraparotid lymphadenopathy may represent metastatic disease from cutaneous primaries or lymphoma 1, 4

Imaging Algorithm

Primary Imaging Modality

MRI with and without IV contrast is the gold standard for comprehensive evaluation, providing detailed information about extent of masses, local invasion, perineural spread, and extension into surrounding structures 1, 4

MRI features suggesting malignancy include:

• T2-hypointensity 1
• Intratumoral cystic components 1
• Infiltrative changes or ill-defined margins 1
• Perineural enhancement or skull base invasion 1

Alternative and Adjunctive Imaging

• Ultrasound (high-frequency ≥12 MHz with color Doppler): Useful for distinguishing parotid versus extraparotid masses and identifying features suspicious for malignancy, but has significant limitations for deep lobe lesions 1, 2
• CT with IV contrast: Use when MRI is contraindicated, particularly useful for evaluating bony details and sialoliths 1, 4
• Avoid as initial studies: Do not order MRA, CTA, FDG-PET/CT, or angiography for initial evaluation of a new parotid mass 1

Critical caveat: Imaging alone cannot definitively distinguish benign from malignant parotid masses—histologic confirmation is essential 1, 4

Tissue Diagnosis

Fine Needle Aspiration Biopsy (FNAB)

FNAB is essential to distinguish salivary gland cancers from non-malignant lesions and should be performed instead of open biopsy for masses at increased risk for malignancy when diagnosis remains uncertain 1

Use ultrasound-guided FNAB rather than palpation-guided to:

• Increase specimen adequacy rates 1, 2
• Target solid components in heterogeneous masses 1
• Improve diagnostic yield and reduce inadequacy rates 1

When FNAB is Inadequate

• Core needle biopsy (CNB): Perform if FNAB is inadequate or for deep minor salivary glands 1, 4
• Repeat ultrasound-guided FNAB: With optimization techniques and on-site cytopathology evaluation 1
• Intraoperative frozen section: Has 99% accuracy for identifying neoplastic lesions, 96% for non-neoplastic, but only 59% for exact malignant tumor type 1, 5

Pathologists should report risk of malignancy using a risk stratification scheme 1

Differential Diagnosis Considerations

Malignant Neoplasms

• Primary salivary gland malignancies (acinic cell carcinoma most common) 3
• Lymphoma (particularly in patients with Sjögren's syndrome or bilateral involvement) 2, 4, 5
• Metastatic disease from cutaneous primaries (examine head and neck skin carefully, especially in elderly patients) 1

Benign Neoplasms

• Pleomorphic adenoma (most common overall, 36.4% of cases) 3
• Warthin's tumor (most common in males, with increasing incidence) 3

Non-Neoplastic Conditions

• Bacterial parotitis (requires immediate antibiotics, gland massage, warm compresses, sialogogues, and aggressive hydration) 2
• Sjögren's syndrome (bilateral parotid involvement with recurrent swelling, associated sicca symptoms) 2
• Intraparotid lymph node hyperplasia 4

Surgical Management Principles

For Confirmed Malignancy

Open surgical excision is the standard, with extent depending on tumor characteristics 1:

• Low-grade, early-stage tumors (T1-T2): Partial superficial parotidectomy may be sufficient 1
• High-grade or advanced tumors: At least superficial parotidectomy with consideration of total/subtotal parotidectomy 1
• Facial nerve preservation: Preserve when preoperative function is intact and a dissection plane can be created between tumor and nerve 1
• Facial nerve resection: Resect involved branches when preoperative facial nerve movement is impaired or branches are encased or grossly involved by confirmed malignancy 1

Neck Management

• Sentinel lymph node biopsy or neck dissection: Consider for high-grade tumors or clinically positive nodes 1
• Adjuvant radiation therapy: Plan for tumors ≥2 cm, high-grade histology, or positive margins 1

Surveillance and Follow-Up

For confirmed malignancy, imaging surveillance must be maintained beyond 5 years due to late recurrence risk, particularly for adenoid cystic carcinoma 1

• Yearly chest CT: Recommended for high-grade histology or poor prognostic features beyond 5 years 1
• Clinical follow-up frequency: Decreases over time but remains essential 1

Common Pitfalls to Avoid

• Never rely solely on imaging to determine benign versus malignant nature—histologic diagnosis is required 1, 4
• Do not underestimate deep lobe involvement when using ultrasound alone 1
• Avoid making decisions about facial nerve sacrifice based on indeterminate diagnoses 1
• Do not proceed directly to open biopsy or surgical excision without attempting FNAB first 1
• Consider lymphoma in the differential: Frozen sections during surgery can prevent unnecessary extensive parotidectomy in 89% of lymphoma cases 5
• Examine skin carefully: Intraparotid lymphadenopathy may represent metastatic disease from cutaneous primaries 1