Case 1.
Differentiation submandibular gland masses from lymph nodes
Küttner Tumor: IgG4-Related Disease of the Submandibular Gland
- Characteristically involves the submandibular glands
- Diffuse enlargement of the submandibular glands that demonstrates homogeneous density or signal intensity at CT and MRI
- Radiologically indistinguishable from primary neoplasm
Key points:
Submandibular space (SMS) is a suprahyoid vertical horse-shoe shaped space below the mylohyoid sling. Major internal contents of the SMS include submandibular gland (SMG), level I lymph nodes, anterior digastric belly muscle and fat.
The first step in evaluating the masses found in SMS is the determination of their origin in SMS, whether intra- or extraglandular.
Features that indicate intragladular origin are :
- ''Beaking" of SMG around mass
- No visible fat plane is seen between the mass and the SMG
- Facial vein is a useful landmark for distinguishing an intraglandular mass from an extraglandular one. Masses, located medial to facial vein, indicate a primary SMG disease.
Pitfalls:
When SMG is operated (neck dissection) and the patient history is unknown, a metastatic lymph node located in the region of gland may look like a SMG mass.
Case 2.
Differentiation parotid masses from the lymph nodes
Key points:
The parotid gland is bordered laterally by platysma muscle, posteriorly by the sternocleidomastoid muscle (SCM), and inferomedially by the posterior digastric muscle.
Evaluating the location of parotid tail masses and their relation to SCM and platysma muscles is of great importance for diagnostic process. Parotid tail masses located anterolateral to the SCM and deep to the platysma muscle. The lymph nodes located anteromedial to the SCM.
Pitfalls:
Warthin’s tumors, usually located in parotid tail, may resemble a lymph node, especially when it is small. Approximately 20% of them are multiple and may be bilateral. Lack of cervical lymph nodes may be a clue. But although rare, there may be extraglandular Warthin's tumors.
Parotid nodes are first order nodal station for skin squamous cell carcinoma (SCC) and melanoma from scalp, auricle, and face. They usually present with multiple, unilateral or bilateral masses with invasive margins, and often central necrosis.
Parotid gland may have primary nodal non-Hodgkin lymphoma (NHL) and systemic NHL metastases. Multiple and bilateral lesions with cervical lymph nodes is a clue.
Case 3.
Differentiation nerve sheath tumors from lymph nodes
Key points:
Neurogenic tumors of the head and neck mainly include schwannomas and neurofibromas which may arise from any cranial nerve or spinal root. The patients are usually asymptomatic or may have minor symptoms.
Features that indicate nerve sheath tumors :
- Well-circumscribed, fusiform or dumbbell-shaped mass
- When paraspinal, smooth enlargement of the bony neural foramen
- Internal cystic changes (most commonly seen in schwannomas)
- Central area of low intensity surrounded by hyperintense peripheral rim on T2-weighted images ‘target sign’ ( commonly related to neurofibromas)
- Lack of flow voids
- Smooth bony remodeling (especially seen in large masses)
Looking for imaging features of an any associated syndromes such as neurofibromatosis type 1 or neurofibromatosis type 2 and getting patient history and physical examination findings is very helpful.
Nerve sheath tumors are slow growing lesions. Demonstrating the lesion on the previous neck CT, MRI or images that include the skull base and neck may be helpful.
Vagus nerve schwannoma separates the internal carotid artery (ICA) and internal jugular vein (IJV), and displace the ICA anteromedially and the IJV posteriorly.
Sympathetic chain schwannomas usually displace the ICA and IJV together, usually without separating them.
Pitfalls:
Schwannomas may mimic hypervascular mass such as paraganglioma. Hypervascular schwannomas show ‘puddling’ of contrast material without arteriovenous shunting on CT angiography.
Case 4.
Differentiation neurogenic tumors of the head and neck from lymph nodes in pediatric patients
Key points:
Neuroblastoma should be considered in an infant with a cervical mass with following features:
- A fast growing mass located posterior to the carotid sheath
- Well-defined, mild to moderately enhancing soft tissue mass with very low ADC
- Presence of multiple cervical metastatic lymph nodes
Ganglioneuroma is benign, well-circumscribed, slow growing tumor which is rarely found in the cervical region. By evaluating asymptomatic children with slow growing neck mass, this tumor should be kept in mind, because of the lack of any specific radiologic finding.
Case 5.
Differentiation hypervascular tumors from lymph nodes
Key points:
Paragangliomas of the head and neck region are highly vascular tumors and typically present in characteristic locations. The most common anatomic locations include the carotid bifurcation (carotid body tumors), along the course of the vagus nerve (vagal paraganglioma), jugular fossa and tympanic cavity (jugulotympanic paragangliomas).
Paragangliomas may have multiple black dots ("pepper") indicating high-velocity flow voids from feeding arterial branches and intense enhancement on MRI.
Hypervascular metastatic neck nodes, including papillary thyroid cancer, medullary thyroid carcinoma, renal cell carcinoma, Caposi sarcoma metastases, may also have similar apperance. They are usually multiple and may have cystic change and calcification.
Papillary thyroid cancer is most common cause of hypervascular metastatic lymph nodes in head and neck region. Thyroid cancer nodal metastasis may also present as a cystic lesion, or a hypervascular, calcific lesion that resemble the primay tumor on the thyroid gland.
Case 6.
Differentiation cystic neck masses from lymph nodes
Key points
Cystic masses of neck constitute a complex group of disorders. Congenital and inflammatory-infectious diseases are commonly seen especially in children. In the evaluation of cystic neck masses in children, patient’s age and clinical history are the most significant clues. These lesions generally have characteristic physical examination findings which may help narrow down the differential diagnosis list.
Location of the cystic lesion may help differentiation. The second branchial cleft cyst is located posterior to the SMG, anterior to the SCM and lateral to the carotid space.
Thyroglossal duct cyst is typically present as a midline fluid collection that may embedded in strap muscles and crossing the hyoid bone. They may be paramidline at infrahyoid level. They located at any level from the base of the tongue to the isthmus of the thyroid gland .
Laryngocele is a cystic dilatation of laryngeal ventricle. It is typically seen as a well-defined, air or fluid-filled lesion related to the paraglottic space, which has continuity with the laryngeal ventricle.
Necrotic lymph node metastases of head and neck tumors are usually seen in adults. These metastatic primer tumors include papillary thyroid cancer and head and neck SCC. Necrotic nodes are located superficial to strap muscles. They may have enhancing solid or nodulary component.
Pitfalls:
Infected second branchial cleft cyst is hard to differentiate from an infected or suppurative lymph nodes. Both have identical clinical and laboratory findings, thick rim enhancement, peripheral fat stranding and associated enlarged lymph nodes. Branchial cleft cysts, sinus or fistulas are congenital lesions and present at birth but may be asymptomatic until become infected. Demonstrating the cystic lesions on prior imaging studies help diagnosis. Recurrence of the infection at the same location and presence of the pits on skin may also helpful.
Case 7.
Differentiation cutaneous and subcutaneous masses from lymph nodes
Key points
Cutaneous and subcutaneous masses are superficial to platysma muscle. These lesions are usually small and diagnosed clinically or more commonly identified incidentally on imaging.
Trichilemmal cyst is benign, lobulated, cyst which is generally located within the scalp. The underlying bone is usually intact. Due to the cystic components contain proteinaceous material, the mass shows hyper-isointensity compare to brain parenchyma on T1-weighted images. T1 signal of the mass is a clue for differentiating trichilemmal cyst from epidermal inclusion cyst. Foci of calcification is seen on CT imaging as an indication of keratin content.
Epidermal inclusion cyst has characteristically round, well-circumscribed appearance with a sclerotic margin. These lesions may cause bone remodeling. Content of the cyst is similar to CSF.