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Dermoid Cyst


KEY FACTS

Terminology

  • Benign, ectopic, squamous epithelial cyst containing dermal elements, including hair follicles and sebaceous and sweat glands

Imaging

  • Midline unilocular cystic lesion with fat

    • Subarachnoid fatty droplets if ruptured

  • Suprasellar or posterior fossa most common intracranial sites

  • Extracranial sites = spine, orbit

    • May have fistulous connections to skin (dermal sinus tract)

  • CT hypodensity (fat)

    • 20% capsular Ca++

  • MR: T1 hyperintense

    • Fat-suppression sequence confirms lipid elements

    • Fat-fluid level in cyst and in ventricles (if ruptured)

  • With rupture: Extensive leptomeningeal enhancement possible from chemical meningitis

Top Differential Diagnoses

  • Epidermoid cyst

  • Craniopharyngioma

  • Teratoma

  • Lipoma

Clinical Issues

  • Rare: < 0.5% of primary intracranial tumors

  • Intradural dermoid cysts 4-9x less common than epidermoid cysts

  • Rupture can cause significant morbidity/mortality

  • Dermoid + dermal sinus may cause meningitis, hydrocephalus

  • Treatment: Complete surgical excision ± shunt for hydrocephalus

Sagittal graphic of an inferior frontal dermoid
shows a discrete, heterogeneous fat-containing mass with squamous epithelium and dermal appendages. There is a ventricular fat-fluid level
and fat within the subarachnoid spaces
related to the rupture.

Axial NECT shows a hypodense midline fatty mass with focal calcification
characteristic for ruptured dermoid cyst. Note fatty hypodense droplets in the sylvian fissures and subarachnoid spaces
.

T1WI shows classic dermoid cyst is hyperintense
. Note fatty droplets in adjacent sylvian fissure
typical for ruptured dermoid.

Axial FSE T2WI in the same patient shows that the mass
is hyperintense but internally heterogeneous. Ruptured dermoid cyst was confirmed at surgery.

TERMINOLOGY

Synonyms

  • Dermoid inclusion cyst, ectodermal inclusion cyst

Definitions

  • Benign, ectopic, squamous epithelial cyst containing dermal elements, including hair follicles and sebaceous and sweat glands

IMAGING

General Features

  • Best diagnostic clue

    • Midline nonenhancing unilocular cystic lesion with fat

      • –

        Subarachnoid fatty droplets if ruptured

  • Location

    • Suprasellar, parasellar

    • Less common in posterior fossa: Cisterna magna, 4th ventricle, and basal cisterns

    • Extracranial sites = spine, orbit

      • –

        May have fistulous connections to skin (dermal sinus tract)

      • –

        Orbit: Dermolipoma at zygomatico-frontal suture

    • Ruptured: Subarachnoid/intraventricular spread of contents

  • Size

    • Variable

  • Morphology

    • Well-circumscribed, lipid-containing mass

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