Cystic Neck Mass in A Child
Bernadette L. Koch, MD
DIFFERENTIAL DIAGNOSIS
Common
Suppurative Lymph Nodes
Abscess
Thyroglossal Duct Cyst
Lymphatic Malformation
Ranula
2nd Branchial Cleft Cyst
Less Common
1st Branchial Cleft Cyst
Thymic Cyst
Rare but Important
Dermoid and Epidermoid
Teratoma
ESSENTIAL INFORMATION
Helpful Clues for Common Diagnoses
Suppurative Lymph Nodes
Key facts
Pus in lymph node = intranodal abscess
Imaging
Thick enhancing nodal walls with central hypodensity
Edema in surrounding fat (cellulitis)
± thickening of muscles (myositis)
Associated nonsuppurative adenopathy
Nontuberculous mycobacterial adenitis lacks surrounding inflammatory changes
Abscess
Key facts
Superficial abscesses: Anterior or posterior cervical or submandibular space
Deep neck abscesses: Retropharyngeal, parapharyngeal, or tonsillar; may grow rapidly airway compromise, ± mediastinal extension
If anterior to left thyroid lobe, think 4th branchial apparatus anomaly
Exclude dental infection and salivary gland calculus as cause of H&N infection
Imaging
Wide prevertebral soft tissue = cellulitis and edema ± frank abscess
False-positive in children if neck not in extended position
Rim-enhancing mass with low-attenuation center; majority drainable pus, up to 25% may be phlegmon without drainable pus
Edema in surrounding fat (cellulitis), ± thickening of muscles (myositis), occasionally air in abscess cavity
Thyroglossal Duct Cyst
Key facts
Remnant of thyroglossal duct, anywhere from foramen cecum at base of tongue to thyroid bed in infrahyoid neck
Treatment = resect cyst, tract, and midline hyoid bone (Sistrunk procedure)
Imaging
Cyst with minimal rim enhancement
At hyoid > suprahyoid = infrahyoid
Most in suprahyoid neck are midline; may be paramidline in infrahyoid neck
Infrahyoid embedded in strap muscles
May contain hyperechoic debris without hemorrhage or infection
Increased enhancement and surrounding inflammatory change when infected
± nodularity or calcifications if associated thyroid carcinoma (adults)
Lymphatic Malformation
Key facts
Congenital vascular malformation
Variably sized lymphatic channels
Present at birth
Grows with child
Imaging
Unilocular or multilocular; macrocystic or microcystic
1 space or trans-spatial
Only septations enhance, unless associated with venous malformation
Lack high-flow vessels on flow sensitive MR sequences and angiography
Fluid-fluid levels
Ranula
Key facts
Simple = postinflammatory retention cyst with epithelial lining; arising in sublingual gland or minor salivary gland, in sublingual space (SLS)
Diving = extravasation pseudocyst when ruptures out of SLS into submandibular space (SMS)
Imaging
Simple = well-defined cyst in SLS
2nd Branchial Cleft Cyst
Key facts
Characteristic location = at or inferior to angle of mandible, posterolateral to submandibular gland, lateral to carotid space, and anteromedial to sternocleidomastoid muscle (SCM)
Uncommon locations = parapharyngeal space, beaking in between internal and external carotid artery, anterior surface of infrahyoid carotid space
Imaging
Well-defined unilocular cyst in typical location
No significant contrast enhancement unless infected
Helpful Clues for Less Common Diagnoses
1st Branchial Cleft Cyst
Key facts
Remnant of 1st branchial apparatus
In or superficial to parotid gland, around pinna or external auditory canal
May extend to angle of mandible
Proximity to facial nerve important for surgical planning
Imaging
Well-defined nonenhancing cyst; contrast-enhancing wall with surrounding inflammation if infected
Thymic Cyst
Key facts
Remnant of thymopharyngeal duct
3rd branchial pouch remnant
Wall contains Hassall corpuscles
Imaging
Cystic neck mass along course of thymopharyngeal duct
± solid enhancing thymic tissue
Closely associated with carotid sheath
May be connected to mediastinal thymus
Rarely ruptures into parapharyngeal space
Helpful Clues for Rare Diagnoses