What is the diagnosis and treatment approach for a parotid gland mass?

Parotid Gland Mass: Diagnostic and Treatment Algorithm

Initial Imaging

MRI with and without IV contrast is the preferred imaging modality for evaluating any parotid gland mass, providing comprehensive assessment of tumor extent, deep lobe involvement, perineural spread, and invasion into surrounding structures 1, 2.

• Ultrasound can serve as an initial screening tool to distinguish parotid from extraparotid masses and identify suspicious features, but has significant limitations in visualizing deep lobe lesions 1, 3.
• CT with IV contrast is reserved for situations where MRI is contraindicated, and is particularly useful for evaluating bony involvement and sialoliths 1.
• FDG-PET/CT should not be used as an initial imaging study but has value for staging and surveillance once malignancy is confirmed 1.

Key Clinical Features to Assess

Red flags suggesting malignancy include pain, facial nerve palsy, trismus, rapid growth, and fixed/hard consistency on examination 1.

• Painless, slowly growing masses can be either benign or malignant, as malignant tumors often mimic benign behavior by displacing rather than infiltrating structures 4.
• Facial nerve weakness (cranial nerve VII dysfunction) strongly suggests malignancy or nerve involvement 2.
• Associated lymphadenopathy with systemic symptoms (fever, weight loss, night sweats) raises concern for lymphoma or metastatic disease 2.

MRI Features Suggesting Malignancy

Imaging alone cannot definitively distinguish benign from malignant lesions, but certain features increase suspicion for malignancy 1, 4:

• T2-hypointensity (low signal on T2-weighted sequences) 1
• Infiltrative changes or ill-defined margins 1, 4
• Intratumoral cystic components 1
• Abnormal apparent diffusion coefficient values on diffusion-weighted imaging 1
• Perineural spread and lymph node involvement 4

Tissue Diagnosis

Fine needle aspiration biopsy (FNAB) is essential and should be performed on all parotid masses to distinguish malignant from benign lesions 1, 2.

• FNAB has limited sensitivity (only 12% in one series) but remains the primary diagnostic method 5.
• Core needle biopsy (CNB) should be performed if FNAB is inadequate or inconclusive 1, 2.
• Pathologists must report risk of malignancy using a standardized risk stratification scheme 1.
• When FNAB and imaging remain inconclusive but lymphoma is suspected, surgical tissue sampling with frozen section analysis can prevent unnecessary extensive surgery (avoided in 89% of cases in one series) 5.

Treatment Algorithm Based on Diagnosis

For Histologically Confirmed Malignancy

Open surgical excision is the standard treatment, with extent determined by tumor grade and stage 1:

• Low-grade, early-stage tumors: 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 management: Preserve the nerve when preoperative function is intact and a dissection plane can be created between tumor and nerve 1
• Facial nerve resection: Indicated only when preoperative facial nerve movement is impaired or branches are encased/grossly involved by confirmed malignancy 1

For Lymphoma

Chemotherapy ± radiation is the treatment of choice, avoiding unnecessary parotidectomy 2, 5.

• 5-year disease-specific survival is 100% for early stages (I-II) and 75% for advanced stages (III-IV) 5

For Inflammatory Conditions

Immunosuppressive therapy with glucocorticoids is first-line for inflammatory conditions like granulomatosis with polyangiitis 3.

• Surgical intervention is reserved only for urgent decompression due to life- or organ-threatening compression 3
• For infectious sialadenitis with reactive lymphadenopathy, medical management with antimicrobials and anti-inflammatory therapy is appropriate 2

For Recurrent Disease

Revision resection with appropriate reconstruction and rehabilitation is recommended for recurrent locoregional disease without distant metastases 1.

Critical Pitfalls to Avoid

• Never rely solely on imaging to determine benign versus malignant nature—histologic diagnosis is mandatory 1, 3.
• Do not make decisions about facial nerve sacrifice based on indeterminate diagnoses—confirm malignancy and direct nerve involvement first 1.
• Do not underestimate deep lobe involvement when using ultrasound alone—MRI is essential for complete assessment 1.
• Do not initiate surgical intervention for inflammatory conditions before attempting appropriate medical therapy 3.
• Do not fail to consider intraparotid nodal metastases in high-grade or advanced parotid cancers 1.