Topographic anatomy and ducts
Major salivary glands are represented by three pairs. Each has its own anatomical features of location and secretion outflow pathways:
- Parotid gland (glandula parotidea). Its excretory duct pierces the buccinator muscle. The opening of the duct is located on the buccal mucosa, forming a papilla precisely at the level of the first upper molar.
- Submandibular gland (glandula submandibularis). Anatomically, it wraps around the posterior free margin of the mylohyoid muscle (m. mylohyoideus). Its excretory pathway—Wharton's duct—runs between the hyoglossus and mylohyoid muscles. It opens on the floor of the oral cavity, located behind the lower incisors on either side of the lingual frenulum.
- Sublingual gland (glandula sublingualis). It is localized in the anterior part of the floor of the oral cavity, positioned above the m. mylohyoideus. Secretions are drained either through a single large Bartholin's duct or via multiple minor ducts directly onto the floor of the oral cavity. Sometimes they empty into the terminal part of the submandibular duct.
Salivary Gland Tumors
Primary tumors are divided into benign and malignant (adenoid cystic carcinoma, acinic cell carcinoma, mucoepidermoid carcinoma, adenocarcinoma, and lymphoma). The probability of malignancy depends on the location:
- In the parotid gland, benign processes predominate. Typical representatives include pleomorphic adenoma and Warthin tumor (often bilateral, multifocal, with a cystic structure, characteristic of smoking patients).
- In the submandibular gland, the ratio of benign to malignant neoplasms is approximately 50/50.
- In the sublingual gland, the vast majority of detected lesions are malignant.
A special condition is the «diving» ranula — a secondary volumetric formation. This is a sublingual gland mucocele that herniates through a congenital defect or the edge of m. mylohyoideus into the submandibular region. On ultrasound, it is visualized as a cyst with a tail extending toward the sublingual space.
Diagnostic imaging algorithm
Ultrasound (US) serves as the first-line method. Since it is difficult to differentiate cancer from a benign adenoma based on echo patterns, ultrasound must be supplemented with core-needle biopsy or fine-needle aspiration biopsy (FNAC).
When performing an ultrasound, the physician must answer several key questions:
- Location and depth: Does the mass originate from the gland itself or is it adjacent to it? Is it located in the superficial or deep lobe? This is critically important for the parotid gland so that the surgeon can assess the risk of iatrogenic injury to the facial nerve.
- Nature and number: Solid or cystic? Single or multiple? Multiple bilateral lesions may indicate a Warthin tumor (in elderly male smokers) or chronic inflammation.
- Lymph nodes: Is concurrent lymphadenopathy present?
Magnetic resonance imaging (MRI) is used as an adjunct to ultrasound. It is indispensable for assessing the local spread of confirmed cancer, the deep lobe of the parotid gland, and detecting perineural spread (including along the facial nerve).
Sialadenitis: inflammatory conditions
Sialadenitis occurs spontaneously (viral or bacterial infection) or secondarily due to duct obstruction.
- Acute sialadenitis. On ultrasound, the affected gland appears diffusely enlarged, hypoechoic, with a total increase in blood flow (vascularity). A dangerous complication is the formation of intraglandular abscesses—they appear as avascular hypoechoic zones.
- Focal sclerosing sialadenitis (Küttner tumor). It forms focal geographical-shaped hypoechoic zones. Due to its similarity to true tumors, it always requires a biopsy.
- Sjogren's syndrome. An autoimmune disorder accompanied by dry mouth and dry eyes. On ultrasound, the gland is shrunken and contains multiple hypoechoic foci (lymphocytic infiltration). The condition requires monitoring due to the high risk of developing MALT lymphoma.
Briefly: answers to topical questions
Which branches form the plexus of the facial nerve (pes anserinus) within the parotid gland?
The facial nerve plexus within the parotid gland is formed by the upper and lower branches, which divide into five terminal branches. The facial nerve enters the substance of the gland and divides into the upper (pars temporofacialis) and lower (pars cervicofacialis) branches, forming the pes anserinus (pes anserinus).
Terminal branches of the parotid plexus (plexus parotideus):
- Temporal branches (rr. temporales) — innervate the epicranius muscle.
- Zygomatic branches (rr. zygomatici) — travel toward the lateral angle of the eye.
- Buccal branches (rr. buccales) — run toward the midpoint between the ala of the nose and the angle of the mouth.
- Marginal mandibular branch (r. marginalis mandibulae) — runs along the lower border of the mandible.
- Cervical branch (r. colli) — descends vertically down the neck.
Which blood vessels provide the arterial blood supply and venous drainage of the submandibular salivary gland?
The arterial blood supply to the submandibular salivary gland is provided by branches of the facial, lingual, and mental arteries, while venous drainage occurs into the facial vein.
Blood vessels of the gland:
- Glandular branches of the facial artery (rr. glandulares a. facialis) — the main source of blood supply.
- Lingual artery (a. lingualis) — participates in arterial inflow.
- Mental artery (a. mentalis) — an additional source of arterial blood.
- Facial vein (v. facialis) — carries out venous blood drainage from the organ.
What types of biopsy are used for the verification of salivary gland tumors, and what are their diagnostic and technical differences?
Fine-needle aspiration biopsy and core-needle biopsy are used to verify salivary gland tumors. These procedures are performed in conjunction with an ultrasound examination, which is the primary imaging modality.
Types of biopsy used:
- Fine-needle aspiration biopsy (FNAC)
- Core-needle biopsy (core biopsy)
Both methods are used for precise pathomorphological verification of masses, as it is difficult to differentiate benign and malignant processes via ultrasound. Information on the technical and diagnostic differences between these methods is absent in the sources.
The smaller the salivary gland, the higher the risk of malignancy: parotid (the largest) — rarely, submandibular — 50/50, sublingual (the smallest) — most often cancer.
Class and exam questions
Can ultrasound reliably determine whether a salivary gland tumor is benign?
No, the ultrasound features of benign and malignant neoplasms often overlap. For final diagnosis verification, a biopsy (FNAC or core-needle biopsy) is always necessary.
Why is it important for a surgeon to know if the deep lobe is involved in parotid gland tumors?
The facial nerve passes through the parotid gland, topographically dividing it into superficial and deep lobes. A tumor in the deep lobe significantly increases the risk of accidental (iatrogenic) nerve injury during surgery.
What is Küttner tumor?
This is not a true neoplasm, but focal sclerosing sialadenitis. On ultrasound, it can mimic a malignant tumor, so pathomorphological verification is mandatory to rule out cancer.
What else to study on this topic
- Anatomy and evaluation of the facial nerve in the facial canal
- Specifics of pleomorphic adenoma of the salivary gland
- Histological types of salivary gland carcinomas
- Technique for core-needle biopsy and FNAC
- Development of MALT lymphoma in the setting of Sjogren's syndrome
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