The patient with a neck swelling and a normal chest radiograph
A 45-year-old woman presents with a 4-week history of a painless, firm swelling in the left side of her neck, just below the angle of the mandible. She has no fever, no weight loss, and no hoarseness. Examination reveals a 2.5 cm mass that is mobile and non-tender. Flexible nasendoscopy is normal. A chest radiograph is normal. Fine-needle aspiration of the mass yields blood-stained fluid. You are asked to interpret the anatomy of the neck and recommend the next imaging step.
1. Using the anatomical triangles of the neck, where is this mass likely located, and what structures lie in that region?
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Location
- The mass lies just below the angle of the mandible, in the anterior triangle of the neck, specifically the submandibular or carotid triangle.
Boundaries
- The anterior triangle is bounded by the midline, the inferior border of the mandible, and the anterior border of sternocleidomastoid.
- The carotid triangle is bounded by the posterior belly of digastric, the superior belly of omohyoid, and the anterior border of sternocleidomastoid.
Contents of the region
- Vessels: common carotid artery, internal jugular vein, and their branches.
- Nerves: vagus nerve, hypoglossal nerve, and the cervical sympathetic chain.
- Lymph nodes: deep cervical chain, including level II and III nodes.
- Salivary glands: submandibular gland and its duct.
- Other structures: the carotid sheath, the ansa cervicalis, and the thyroid cartilage.
Implications
- A mass here could be a lymph node (reactive, lymphoma, metastatic), a salivary gland lesion, a branchial cleft cyst, or a vascular lesion.
- The blood-stained aspirate raises concern for a vascular or cystic lesion and warrants imaging before any further intervention.
2. What imaging would you request, and how would you use the anatomy to distinguish a branchial cleft cyst from a necrotic lymph node or a carotid body tumour?
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Imaging
- Ultrasound is the first-line investigation: it can confirm cystic versus solid nature, assess vascularity, and guide further sampling.
- Contrast-enhanced CT or MRI is used for deep extension, relationship to vessels, and surgical planning.
Differentiating features
- Branchial cleft cyst (second branchial cleft): typically a well-defined cystic lesion anterior to the sternocleidomastoid muscle, lateral to the carotid sheath, and posterior to the submandibular gland. It may have a thin wall and no internal enhancement.
- Necrotic lymph node: shows a thick, irregular enhancing rim with central low attenuation; may be multiple; associated with primary tumour elsewhere (e.g., head and neck squamous cell carcinoma, lymphoma, tuberculosis).
- Carotid body tumour: splayed internal and external carotid arteries ('lyceum' sign), intense enhancement, and flow voids on MRI. It is located at the carotid bifurcation.
Anatomical landmarks
- The sternocleidomastoid muscle is the key landmark: branchial cysts lie anterior to it, while lymph nodes may lie deep or posterior.
- The carotid sheath lies medial to the cyst.
Practical point
- Blood-stained aspirate is atypical for a simple branchial cyst and raises concern for malignancy; imaging should be followed by excision or core biopsy as appropriate.