Synonyms: Sternocleidomastoid (SCM) tumor of infancy, congenital muscular torticollis

Increased incidence in breech presentation and difficult deliveries

Present with neck mass ± torticollis, usually within 1st 2 weeks of life

Ultrasound preferred imaging modality

Large SCM muscle, focal or diffuse

Almost always unilateral

Variable echogenicity, attenuation, signal intensity; heterogeneous contrast enhancement on MR

No associated adenopathy

No extramuscular extension of mass

“Reactive” implies benign etiology

Acute or chronic

Any H&N nodal group

Response to infection/inflammation

Enlarged oval-shaped lymph nodes

Variable enhancement, usually mild

± enlargement of lingual, faucial, or adenoid hypertrophy

± stranding of adjacent fat (cellulitis)

± edema in adjacent muscles (myositis)

± suppurative nodes or abscess

Vacular neoplasm, NOT malformation

Usually not well seen at birth, more apparent within 1st few weeks of life

Proliferative phase: 1st year of life

Involuting phase: 1-5 years

Involuted usually by 5-7 years

GLUT-1: Specific immunohistochemical marker expressed in all 3 phases of infantile hemangioma; also expressed in placenta, fetal, and embryonic tissue

Congenital hemangioma: Rare variant, present at birth or on prenatal imaging (fetal hemangioma); 2 subtypes, rapidly involuting (RICH) shows involution by 8-14 months, noninvoluting (NICH)

Proliferative: Solid, intensely enhancing mass with intralesional high-flow vessels

Involutional: Fatty infiltration, ↓ size

PHACES syndrome: Posterior fossa abnormalities, hemangiomas, arterial anomalies, cardiovascular defects, eye abnormalities, sternal clefts

Carotid space, perivertebral space (brachial plexus) common

Localized, diffuse, or plexiform

Single or multiple

Localized: Well-circumscribed, smooth, solid masses with variable enhancement

Diffuse: Plaque-like thickening of skin with poorly defined linear branching lesion in subcutaneous fat

Plexiform: Lobulated, tortuous, rope-like expansion in major nerve distribution; “tangle of worms” appearance

Contains all 3 germ layers

Mature or immature, rarely malignant in neonate

Large, heterogeneous mass

Frequently with fat and calcium

Solid and cystic components

Acute disseminated form (Letterer-Siwe) occurs in children < 1 year

Acute onset of hepatosplenomegaly, rash, lymphadenopathy, marrow failure

Skeletal involvement may be absent

Large nonspecific cervical lymph nodes

Hepatosplenomegaly

Most cervical disease is metastatic from retroperitoneal primary lesion

Metastatic cervical disease more common in older children

Large metastatic lymph nodes

Bilateral skull base metastasis common

Skull base metastases: Enhancing masses with osseous erosion ± intracranial or intraorbital extension

Synonyms: Desmoid or aggressive fibromatosis, infantile fibromatosis, extraabdominal desmoid tumor

Benign soft tissue tumor arising from musculoaponeurotic structures

Tendency to infiltrate adjacent tissues

Recurrence common

Does not metastasize

Identified at all ages

In infants, more common in retroperitoneum and extremity

Well-defined or poorly marginated, infiltrative mass

Often trans-spatial enhancing mass

± erosion of adjacent bone

< 5% are primary cervical lesions

In general, < 1 year = better prognosis

Young children may present with opsoclonus-myoclonus

Solid mass closely associated with carotid sheath space

Calcifications common

Foraminal or intraspinal extension

Remnants along thymopharyngeal duct

Mildly enhancing soft tissue mass