23.2 Salivary Glands & Neck Lymph Nodes
Key Takeaways
- The parotid, submandibular, and sublingual glands are the major salivary glands; the parotid is normally homogeneous and hyperechoic because of its fat content
- Sialolithiasis most often affects the submandibular gland and Wharton duct, appearing as an echogenic focus with posterior shadowing and proximal ductal dilation
- Pleomorphic adenoma, the most common parotid tumor, is a well-defined hypoechoic solid mass; Warthin tumor occurs in older male smokers and often contains cystic components
- A normal lymph node is oval (reniform) with an echogenic fatty hilum; round shape, loss of the hilum, microcalcifications, cystic change, and peripheral vascularity are suspicious for metastasis
- Microcalcifications or cystic change within a cervical node strongly suggest metastatic papillary thyroid carcinoma
Salivary Gland Anatomy and Technique
The three paired major salivary glands are scanned with a high-frequency linear transducer (7.5–15 MHz), just as for the thyroid. The parotid gland is the largest, lying over the masseter muscle and wrapping around the posterior mandibular ramus and external auditory canal; it is divided by the facial nerve into superficial and deep lobes, although the nerve itself is not seen — the retromandibular vein and external carotid artery serve as the sonographic boundary. The submandibular gland sits in the submandibular triangle below the mandible body, wrapping around the posterior edge of the mylohyoid muscle. The sublingual glands are the smallest, lying in the floor of the mouth above the mylohyoid, and are best assessed with the chin lifted. Normal parotid parenchyma is homogeneous and hyperechoic (it contains abundant fat) and slightly more echogenic than the submandibular gland, which is more homogeneous and less fatty. Stensen duct drains the parotid across the masseter into the mouth opposite the second upper molar; Wharton duct drains the submandibular gland forward into the floor of the mouth. Normal ducts are thin and barely visible unless dilated.
Sialolithiasis and Sialadenitis
Sialolithiasis (salivary stone disease) is the most common salivary gland abnormality and most often involves the submandibular gland and Wharton duct — roughly 80–90% of stones — because its secretions are more mucinous and alkaline and the duct courses uphill against gravity. On ultrasound a stone appears as a bright echogenic focus with clean posterior acoustic shadowing, and a stone obstructing the duct produces proximal ductal dilation (a duct wider than about 2–3 mm is dilated). Clinically the patient has painful gland swelling that worsens with eating, when saliva production surges.
Sialadenitis is inflammation of the gland, usually from obstruction or infection. Acute sialadenitis shows an enlarged, hypoechoic, hyperemic gland, sometimes with ductal dilation and debris; an abscess appears as a complex fluid collection with peripheral flow and no internal vascularity. Chronic sialadenitis produces a small, heterogeneous, fibrotic gland.
Salivary Tumors
Most salivary tumors occur in the parotid, and most parotid tumors are benign.
| Tumor | Typical patient | Sonographic appearance | Notes |
|---|---|---|---|
| Pleomorphic adenoma | Middle-aged adults | Well-defined, lobulated, hypoechoic solid mass, often with posterior enhancement | Most common parotid tumor; can recur or rarely undergo malignant transformation if incompletely excised |
| Warthin tumor | Older male smokers | Well-defined mass, frequently with cystic components | Second most common benign parotid tumor; may be bilateral or multifocal; located in the lower pole near the tail |
| Mucoepidermoid carcinoma | Variable | Solid mass with irregular or ill-defined margins, internal cystic areas | Most common malignant salivary tumor |
| Adenoid cystic carcinoma | Older adults | Infiltrative solid mass | Notable for perineural spread |
A key exam distinction: pleomorphic adenoma = most common parotid tumor overall, a well-defined hypoechoic solid lesion; Warthin tumor = older male smokers, classically with cystic areas and sometimes bilateral.
Sjögren syndrome is an autoimmune exocrinopathy that attacks the salivary and lacrimal glands. Sonographically the parotid and submandibular glands become heterogeneous with multiple small hypoechoic or cystic areas in a "salt-and-pepper" or honeycomb pattern, reflecting lymphocytic infiltration. Patients have dry mouth (xerostomia) and dry eyes, and there is an increased long-term risk of lymphoma.
Lymph Node Assessment
Cervical lymph nodes are evaluated with the same high-frequency linear probe, sweeping through the standard neck regions. Node morphology matters more than size alone.
A normal or reactive node is:
- Oval or reniform (kidney-bean shaped), with a long-axis to short-axis ratio greater than about 2
- Surrounded by a thin hypoechoic cortex
- Centered on an echogenic fatty hilum
- Vascularized in a hilar pattern — vessels enter at the hilum and branch orderly outward
Suspicious features for metastatic or malignant involvement include:
- Round shape (short-axis enlargement out of proportion to the long axis)
- Loss or displacement of the echogenic hilum
- Punctate microcalcifications — strongly associated with metastatic papillary thyroid carcinoma
- Cystic (anechoic) change within the node — also characteristic of papillary thyroid metastases
- Peripheral or mixed vascularity — chaotic vessels entering at the capsule rather than the hilum
- Matting, extracapsular spread, or invasion of adjacent vessels
Reactive nodes from infection or inflammation are enlarged but retain the oval shape, fatty hilum, and hilar vascularity. Lymphomatous nodes tend to be round, markedly hypoechoic (sometimes almost pseudocystic with posterior enhancement), and often form large confluent groups; they usually lose the fatty hilum but may show prominent internal flow. Tuberculous nodes can be necrotic and matted.
Neck Levels Basics
Clinicians localize nodes by surgical neck levels, which the sonographer should reference in reports:
- Level I — submental and submandibular triangles (oral cavity, lip, anterior mouth floor drainage)
- Level II — upper jugular chain, from the skull base to the hyoid (a common site for oropharyngeal and metastatic nodes)
- Level III — mid-jugular chain, hyoid to cricoid
- Level IV — lower jugular chain, cricoid to clavicle (thoracic and abdominal malignancies, especially on the left)
- Level V — posterior triangle, behind the sternocleidomastoid (nasopharyngeal and thyroid cancers, lymphoma)
- Level VI — central compartment, around the thyroid and trachea (thyroid carcinoma drainage)
When a suspicious node is found, the study should document its level, short-axis dimension, shape, hilum status, internal architecture (calcification, cystic change), and Doppler pattern, and the primary gland — thyroid, salivary — should be searched for a source lesion.
A patient has painful swelling below the jaw that worsens with meals. Sonography shows an echogenic focus with posterior shadowing inside a dilated duct near the submandibular gland. Which gland is most commonly affected by this condition?
A 68-year-old man with a long smoking history has a painless mass at the lower pole of the parotid. Sonography shows a well-defined mass with internal cystic components. The contralateral parotid contains a smaller similar lesion. The most likely diagnosis is:
Which cervical lymph node feature is MOST suspicious for metastatic papillary thyroid carcinoma?