Germinoma

KEY FACTS

TERMINOLOGY

• Intracranial germ cell tumor (iGCT)

• iGCTs are intracranial homologue of gonadal germinomas

(ovarian dysgerminoma, testicular seminoma)

IMAGING

• Most common: In/near midline (80-90%)

○ Pineal region ~ 50-65%

○ Suprasellar ~ 25-35%

• Less common: Basal ganglia/thalami ~ 5-10%

• 20% multiple

○ Most common = pineal with suprasellar

• Pineal germinoma

○ Hyperdense pineal region mass engulfs pineal Ca++

○ Strong, often heterogeneous enhancement

○ T2/FLAIR hyperintensity in surrounding brain =

inflammation/granulomatous change

• Suprasellar germinoma

○ Absent posterior pituitary "bright spot"

○ "Fat" stalk/pituitary gland

○ Strong, relatively uniform enhancement

○ May have cysts, hemorrhage (rare)

• Basal ganglia germinoma

○ Rare; hemorrhage common

TOP DIFFERENTIAL DIAGNOSES

• Pineal germinoma

○ Pineocytoma, other pineal GCTs

• Suprasellar germinoma ("fat" infundibulum)

○ Adult = neurosarcoid, metastases

○ Child = Langerhans cell histiocytosis (LCH)

CLINICAL ISSUES

• 90% of patients < 20 years old

○ Pineal region germinoma: M:F ~ 10:1

○ Causes dorsal midbrain syndrome

DIAGNOSTIC CHECKLIST

• Child with diabetes insipidus? Think germinoma or LCH!

(Left) Sagittal graphic shows

synchronous germinomas in

the suprasellar and pineal

regions. Note the

cerebrospinal fluid spread of

tumor in the lateral, 3rd, and

4th ventricles ﬈. (Right) Axial

NECT scan shows typical

findings of pineal germinoma

with a well-demarcated

slightly hyperdense mass ſt

engulfing the calcified pineal

gland ﬇.

(Left) Axial T2WI in a 14-yearold boy with visual symptoms

shows a suprasellar mass ﬈

that is slightly hypointense

relative to gray matter. A 2nd,

smaller mass ﬉ is present in

the pineal gland. (Right) T1 C+

MR in the same patient shows

that the lobulated suprasellar

mass ﬈ enhances strongly.

The pineal mass ﬉ also

enhances uniformly. The

combination of suprasellar

and pineal mass (sometimes

called "double midline"

germinoma) occurs in ~ 20%

of cases.

Brain: Pathology-Based Diagnoses: Neoplasms,

Cysts, and Disorders

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