Case study head and neck Gerrit Engelbrecht Department radiology UFS

Case 24 year old male Refered from ophtalmology MRI and CT Fluctuating mass, painless, left temporal region.( aware of it for several months, insidious in onset ) Mild proptosis of the left eye. No visual field fallout. No cranial nerve fallout. Normal movement of the globe. Neurological exam normal. No systemic illnesses. No histology available MRI and CT

T2* FGRE

T2 Ax

T2 Flair

Sag T1

AxT1-fs SE S 3mm

Cor T1-fs SE S 4 mm

AxT2 FSE H 3 mm

Ax T1 SE + C

Cor T1 +C FS SE 4 mm

Ax T1+ C FS SE S 3 mm

Scout of CT

CT pre and post contrast

General features Best diagnostic clue: Location Cystic, well-demarcated, anterior extraconal mass with fatty, fluid or mixed contents Location Tethered to orbital periosteum, near suture lines Majority extraconal in superolateral aspect of anterior orbit, at frontozygomatic suture (65-75%) Remainder mostly in superonasal aspect, at frontolacrimal suture, but can occur anywhere

Size Morphology Typically less than 1-2 cm in superficial lesions Larger in deep, complicated lesions Morphology Ovoid, well-demarcated cystic mass Most show thin definable wall (75%) No nodular soft tissue outside cyst (80%)

Contents Internal fat or fluid features; may be mixed or contain debris Lipid components evident in 40-50% of lesions Fluid-fluid levels in 5 % of lesions Dermoid cysts typically but not exclusively contain fat and appear more heterogeneous Epidermoid cysts typically have features similar to fluid and appear more homogeneous

Subtypes Superficial (simple, exophytic) Typically smaller, discrete, rounded Present in early childhood Deep (complicated, enclophytic) More insidious, frequent bony changes May extend into sinuses, high deep masticator space, or intracranially

Radiographic findings Scalloped bony lucency with sclerotic margins

CT Findings NECT CECT Hypodense fat in about half Calcification in 15% Density -30 to -80 HU Calcification in 15% Fine or punctate, in cyst wall osseous remodeling in majority of lesions (85%) Pressure excavation; smooth, scalloped margins Thinning of bone, may cause focal dehiscence Bony tunnel, cleft, or pit in up to one-third, leading to “dumbbell appearance Irregular margins indicate rupture and inflammatory reaction Bony changes less common in superficial lesions CECT Mild, thin, rim-enhancement Irregular inflammatory enhancement if ruptured

MR Findings T1WI T2WI TI C+ Diffusion and FLAIR Strongly hyperintense (cf vitreous) if fatty contents Isointense or slightly hyperintense otherwise T2WI Isointense or mildly hypointense (cf vitreous) Heterogeneous debris TI C+ Thin rim-enhancement More extensive inflammation if ruptured Diffusion and FLAIR Epidermoid cysts show high signal as in other areas of CNS imaging

Ultrasonographic findings Adequate for evaluation of simple superficial lesions without posterior extension High internal reflectivity, variable attenuation Debris may impair determination of cystic nature

Pathology (general features) Developmental mass, non-neoplastic contents Epidermoid: Desquamated keratinaceous debris, cholesterol; thin capsule Dermoid: Keratin, sebaceous secretions, lipid metabolites, hair; fibrous capsule

Etiology Congenital inclusion of dermal elements at site of embryonic suture closure Sequestration of trapped surface ectoderm

Epidemiology Present from birth; spontaneous occurrence 10% of head and neck dermoid and epidermoid cysts are periorbital 5% of orbital masses

Gross pathological features Whitish, well-delineated mass Connected to orbital periosteum by fibrovascular tissue Oily or cheesy material that is tan, yellow, or white May contain blood or chronic blood products

Microscopic features Dermoid Epidermoid Contains dermal structures, including sebaceous glands and hair follicles, blood vessels, fat and collagen within a fibrous capsule Sweat glands in minority (20%) Lined by keratinizing squamous epithelium Epidermoid Inner surface of thin capsule lined by keratinizing, stratified epithelium Half show disruption of lining indicating rupture at some point Inflammatory changes in 40% Granulomatous reaction, particularly in deep, complicated lesions

Presentation Most common signs/symptoms: Subcutaneous nodule near orbital rim Smaller, little globe displacement Painless subcutaneous mass (85-90%) Clinical profile Adult presentation Nontender, firm; painless in 90% Fixed to underlying bone (cf sebaccous cyst) More commonly arises deep to orbital rim Often near the lacrimal gland in the extraconal orbit May present with rupture (10-15%) Secondary to trauma or spontaneously Less easily palpated; larger, globe displacement Acute inflammation mimics cellulitis or inflammatory rhabdomyosarcorna Less well-defined borders, more likely to erode into adjacent structures Can result in entrapment, neuropathy Mass effect if very large Acquired epidermoid cysts of skin are common, but not included in this discussion Diplopia due to restricted movement Compromise globe or cranial nerves . Childhood presentation More common than adult

Demographics Age Gender: Equal or slight male predominance Most frequently presents in childhood and teenage Mean age in late teens to twenties Simple, superficial lesions often present in infancy May present or grow at any age Occasionally will appear in adult and grow significantly over several months Gender: Equal or slight male predominance

Natural history and prognosis Benign lesion, usually cosmetic considerations Very slow growth, usually dormant for years Present during childhood but small and dormant Becomes symptomatic during rapid growth phase ¡n young adult Sudden growth or change following rupture Significant inflammation and increased size Rarely fistula may occur

Treatment Surgical resection is curative Entire cyst must be removed to prevent recurrence, including growth center at periosteal interface Approach depends on location in orbit Lesions evident in early childhood should be removed to avoid traumatic rupture Steroids or non-steroidal drugs to calm inflammation in ruptured lesions

References Grainger&Allison’s Diagnostic Radiology, Fifth Edition. Head and neck Imaging, Fourth Edition, Peter M.Som & Hugh D Curtin. Diagnostic imaging, Head and Neck, H. Ric Harnsberger

Differential diagnosis Frontal mucocele Benign (hyperplasia) or malignant (NHL) Associated with chronic inflammatory sinus disease, e.g., polyposis and noninvasive fungal sinusitis Other systemic malignancy Langerhans histiocytosis, leukemia, neuroblastoma Rhabdomyosarcoma Expansile mass arising within frontal sinus Malignancy of children and young adults Idiopathic orbital pseudotumor Invasive mass arising anywhere in orbit Acute onset pain, edema, and proptosis Vascular lesions Infiltrating mass involving any area of orbit Venolymphatic malformation Lacrimal gland neoplasm Capillary hemangiotna (infants) Minor salivary: Adenoid cystic, mucoepidermoid Sebaceous cyst Ovoid; fat density and signal Destructive bony changes in malignant lesions Mobile, attached to the skin Lymphoproliferative lesion Predilection for lacrimal gland, can involve any area