Pediatric Orbital Dermoid

  • Etiology: developmental anomaly in which embryonic ectoderm is trapped in closing neural tube
  • US: dermoid cyst and epidermoid cyst cannot be distinguished between on US, well-circumscribed / avascular / hypoechoic-echogenic debris may represent calcification or fat or mucoid or purulent material, may or may not have sinus tract extending to skin, if there is surrounding hyperemia it is most likely due to chemical inflammation from rupture rather than true infection
  • CT: in upper outer quadrant at fronto-zygomatic suture, fat containing mass forming a fossa in adjacent bone, bony erosion common
  • Clinical: most common orbital mass
    — Epidermoids contain only ectoderm – are lined with squamous epithelium and contain desquamated keratinized debris
    — Dermoids contain only ectoderm – are lined with squamous epithelium and contain dermal structures such as hair follicles and sebaceous/sweat gland elements

Radiology Cases of Orbital Dermoid

CT of orbital dermoid
Axial CT without contrast of the orbits in soft tissue (above) and bone windows (below) show a left superomedial rounded low density mass that is not causing any bone erosion.
CT of orbital dermoid
Coronal (above) and axial (below) CT with contrast of the orbits show a right superolateral rounded low density mass that is not causing any bone erosion.