What is the approach for evaluating and treating parotid gland disorders?

Comprehensive Approach to Parotid Gland Evaluation and Treatment

MRI with and without IV contrast is the preferred imaging modality for evaluating parotid gland disorders as it provides the most comprehensive information about the extent of masses, local invasion, perineural spread, and possible extension into surrounding structures. 1

Initial Evaluation

Clinical Assessment

• Symptoms and signs that suggest malignancy include pain/tenderness, adhesion to surrounding tissues, facial nerve palsy, trismus, and fixation 1, 2
• Malignant tumors have significantly higher incidence of these symptoms compared to benign tumors, with facial nerve palsy observed in 18% of malignant cases but none in benign cases 2
• Clinical history and physical examination findings strongly influence the diagnostic workup and treatment planning 1

Imaging Approach

• Imaging cannot definitively determine if a parotid lesion is benign or malignant, but helps determine:
  • Whether the mass is intraparotid or extraparotid 1
  • Characteristics of the mass 1
  • Presence of additional masses 1
  • Deep lobe involvement 1

Recommended Imaging Modalities:

1. Ultrasound (US)

   • First-line diagnostic approach for initial evaluation 3, 4
   • Excellent for localization of parotid versus extraparotid masses 1
   • Can identify features suspicious for malignancy 1
   • Limitations: deep lobe lesions are not well visualized 1
   • Newer techniques like contrast-enhanced US and elastography show promise for improved differentiation between benign and malignant lesions 3

2. MRI with and without IV contrast

   • Preferred comprehensive evaluation method 1
   • Provides detailed information about:
     • Full extent of the mass 1
     • Deep lobe involvement 1
     • Local invasion 1
     • Perineural tumor spread 1
     • Extension into temporal bone 1
   • MRI characteristics that suggest malignancy include T2-hypointensity, intratumoral cystic components, and apparent diffusion coefficient values 1
   • Limitations: increased time, susceptibility artifacts, and motion artifacts 1

3. CT with IV contrast

   • Commonly used for evaluating palpable parotid abnormalities, especially in suspected acute inflammation 1
   • Better for visualizing bony details and sialoliths compared to MRI 1
   • Shorter examination time than MRI (advantage in children or uncooperative patients) 1

4. Specialized Studies

   • CT or MRI sialography: For detailed assessment of parotid ducts when duct obstruction is suspected 1
   • FDG-PET/CT: Not for initial evaluation but useful for staging and surveillance of parotid malignancy 1
   • PET/CT may be performed for patients with advanced-stage high-grade salivary gland cancers 1

Diagnostic Confirmation

• Tissue biopsy is essential to distinguish salivary gland cancers from non-malignant lesions 1
• Fine needle aspiration biopsy (FNAB) is the primary method 1
• Core needle biopsy (CNB) may be performed if FNAB is inadequate or for deep minor salivary glands 1
• Pathologists should report risk of malignancy using a risk stratification scheme 1
• Ancillary testing (immunohistochemical or molecular studies) may support diagnosis 1

Treatment Approach

Surgical Management

• Open surgical excision is the standard for histologically confirmed salivary gland malignancies 1
• Extent of surgery depends on tumor characteristics:
  • Low-grade, early-stage tumors (T1-T2): Partial superficial parotidectomy may be sufficient 1
  • High-grade or advanced tumors (T3-T4): At least superficial parotidectomy with consideration of total/subtotal parotidectomy 1

Facial Nerve Management

• Preserve facial nerve when preoperative function is intact and a dissection plane can be created between tumor and nerve 1
• Resect involved facial nerve branches when:
  • Preoperative facial nerve movement is impaired 1
  • Branches are encased or grossly involved by confirmed malignancy 1
• Important: Decisions resulting in major harm such as facial nerve resection should not be based on indeterminate preoperative or intraoperative diagnoses alone 1

Neck Management

• Elective neck treatment is recommended over observation for:
  • T3 and T4 tumors 1
  • High-grade malignancies 1
• For elective neck management, ipsilateral selective neck dissection should be performed 1
• For parotid malignancies, levels may include 2-4 1

Postoperative Complications

• Most common complication is temporary facial palsy 5
• Permanent facial palsy occurs more frequently with malignant disease 5
• Risk of complications increases with more extensive surgery 5

Special Considerations

Pediatric Patients

• Age helps narrow differential diagnosis:
  • Vascular and congenital lesions more frequent in first year of life 4
  • Solid tumors more frequent in older children 4
• Ultrasound is first-line diagnostic approach in children 4
• MRI is the imaging modality of choice for investigating nature and extent of lesions 4

Recurrent Disease

• For resectable recurrent locoregional disease without distant metastases, revision resection with appropriate reconstruction and rehabilitation should be offered 1

Common Pitfalls to Avoid

• Relying solely on imaging to determine benign versus malignant nature - histologic diagnosis is usually needed 1
• Underestimating deep lobe involvement when using ultrasound alone 1
• Making decisions about facial nerve sacrifice based on indeterminate diagnoses 1
• Failing to consider intraparotid nodal metastases in high-grade or advanced parotid cancers 1