What further ultrasound (u/s) testing should be ordered for incidental findings of solid parotid gland nodules on computed tomography (CT) orbit?

From the Guidelines

For incidental solid parotid nodules found on CT orbit, ultrasound evaluation of the entire parotid gland with Doppler assessment should be ordered. This recommendation is based on the American Society of Clinical Oncology (ASCO) guideline for the management of salivary gland malignancy, which suggests that imaging, including neck ultrasound, CT with intravenous contrast, and/or MRI of the neck and primary site, should be performed in patients with a suspicion of salivary gland cancer 1.

When ordering the ultrasound, it is essential to include measurement of all nodules in three dimensions, assessment of nodule margins, internal architecture, vascularity, and evaluation for calcifications. The radiologist should also examine adjacent lymph nodes for any abnormalities.

• Ultrasound provides excellent soft tissue resolution without radiation exposure
• Allows real-time assessment of the nodules
• Can help determine if fine needle aspiration (FNA) is necessary
• Risk factors that might prompt FNA include nodules larger than 1.5 cm, irregular margins, heterogeneous echogenicity, increased vascularity, or concerning clinical features like facial nerve involvement or rapid growth, as suggested by the ASCO guideline 1.

Given the potential for malignancy, even in incidental findings, and the importance of early detection and management, ultrasound evaluation is the preferred initial follow-up imaging modality. This approach aligns with the guideline's emphasis on imaging for the characterization of salivary gland masses and the planning of appropriate management, including potential biopsy or further diagnostic procedures 1.

From the Research

Incidental Findings on CT Orbit of Solid Parotid Gland Nodules

For incidental findings on CT orbit of solid parotid gland nodules, further testing is necessary to determine the nature of the nodules.

• The following ultrasound (US) tests can be ordered:
  • Ultrasound imaging: This is a common further investigation for parotid incidentalomas, as seen in 2.
  • Ultrasound-guided fine-needle aspiration cytology (FNAC): This provides higher accuracy and can help avoid repeat sampling and excision biopsy, as stated in 2 and 3.
  • Ultrasound-guided core biopsy: This can provide a definitive diagnosis and is a cost-effective and rapid diagnostic tool, as mentioned in 3.

Diagnostic Approach

The diagnostic approach for parotid gland nodules should consider the following:

• Fine-needle aspiration (FNA) biopsy is useful in the preoperative setting, but its accuracy is highly dependent on operator experience and interpretative skills of the cytopathologist, as noted in 4.
• The results of FNA biopsy should be considered in a global context, in conjunction with clinical and radiographic findings, as stated in 4.
• Ultrasound-guided biopsy can help reduce the risk of non-diagnostic results and provide a more accurate diagnosis, as seen in 5 and 6.

Clinicopathological Features

The clinicopathological features of incidental parotid lesions include:

• A high percentage of benign lesions, with Warthin tumor being the most common diagnosis, followed by pleomorphic adenoma, as reported in 5.
• A low incidence of primary parotid malignant neoplasms, as seen in 5.
• The possibility of metastatic lesions in patients with known malignancy, as noted in 5.