Signs and symptoms of infection

May be in deep soft tissues of neck

May present with airway impingement

75% drainable pus; 25% phlegmonous, nondrainable inflammatory tissue

Low-attenuation, rim-enhancing mass

Retropharyngeal edema common

May extend via danger space into mediastinum

Most common cystic neck mass with spontaneous hemorrhage

Sudden increase in size secondary to hemorrhage or viral respiratory infection

Unilocular or multilocular; macrocystic or microcystic; 1 space or trans-spatial

Insinuates morphology

Only septations enhance, unless associated with venous malformation

Lack high-flow vessels on flow-sensitive MR sequences and angiography

Fluid-fluid levels secondary to intralesional hemorrhage common

Lobulated soft tissue mass; variably sized venous channels with phleboliths

Mass increases in size with Valsalva, crying, or bending over

Intermediate attenuation/hyperintense T2 with variable contrast enhancement

No high flow vessels

Neoplasm with spontaneous proliferation and involution

Present within 1st few weeks of life; usually not present at birth

May be multiple (PHACES syndrome)

Lobulated mass, intense enhancement

High-flow intralesional vessels

Localized neurofibroma (NF), diffuse NF, plexiform NF (PNF), or malignant peripheral nerve sheath tumor (PNST)

If multiple or plexiform, think NF1

May be hypoattenuating on CT

Localized: Well-circumscribed, fusiform, solid masses and moderate enhancement ± dumbbell-shaped extension into neural foramina

Diffuse NF: Plaque-like subcutaneous lesion with poorly defined infiltrating margins, moderate enhancement

Plexiform NF: Lobulated, tortuous, rope-like enlargement in major nerve distribution; resembles “tangle of worms”

Malignant PNST: Benign vs. malignant difficult to differentiate on imaging; consider malignant if ≥ 5 cm, intensely enhancing with infiltrative margins

Sites: Orbit, nasopharynx, temporal bone, sinonasal, cervical neck

Soft tissue mass with variable contrast enhancement ± bone erosion

Coronal post-contrast fat-saturated T1 images best for intracranial extension

Benign neoplasm, mature fat

Well-circumscribed homogeneous mass of fat attenuation and signal intensity

Small minority of lesions will have a nonfatty soft tissue component

Any space of neck

Single space or trans-spatial

Imaging cannot differentiate between lipoma and low-grade liposarcoma

Remnant of thymopharyngeal duct, 3rd branchial pouch remnant

Wall contains Hassall corpuscles

Cystic neck mass along course of thymopharyngeal duct ± solid enhancing thymic tissue

Close association with carotid sheath

May be connected to mediastinal thymus directly or by fibrous cord

Rarely extends to skull base; may rupture into parapharyngeal space

Presents with recurrent thyroiditis or anterior neck abscess secondary to sinus tract extending from apex of pyriform sinus to lower anterior neck

Cyst or abscess anterior to left thyroid lobe with associated thyroiditis

Barium swallow or post barium swallow CT may show sinus tract extending from apex of pyriform sinus to anterior lower neck

All 3 germ cell lines

Mature, immature, and malignant

Fat, calcium, cyst, and solid components

Synonyms: Desmoid fibromatosis, extraabdominal desmoid fibromatosis, infantile fibromatosis

Histologically benign fibroproliferative disorder with potentially aggressive clinical course and invasive growth

Associated with Gardner syndrome

Poorly marginated trans-spatial mass

Moderate post-contrast enhancement

± bone erosion or invasion