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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!

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
.

Axial NECT scan shows typical findings of pineal germinoma with a well-demarcated slightly hyperdense mass
engulfing the calcified pineal gland
.

Axial T2WI in a 14-year-old 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.

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.

TERMINOLOGY

Abbreviations

  • Intracranial germ cell tumor (iGCT)

Synonyms

  • Dysgerminoma, extragonadal seminoma

Definitions

  • iGCTs are intracranial homologue of gonadal germinomas (ovarian dysgerminoma, testicular seminoma)

IMAGING

General Features

  • Best diagnostic clue

    • Hyperdense pineal region mass that engulfs pineal Ca++

    • Suprasellar mass with diabetes insipidus (DI)

    • BG mass with ipsilateral hemiatrophy

  • Location

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

      • –

        Pineal region ~ 50-65%

      • –

        Suprasellar ~ 25-35%

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

    • Other sites: Intraventricular (3rd), intrasellar, bulbar, intramedullary, midbrain, hemispheric

  • Size

    • Varies with location

      • –

        Pineal: Can be large if no hydrocephalus, midbrain compression ± invasion

      • –

        Infundibular stalk: Early presentation with DI common

        • □

          Mass can initially be tiny/imperceptible

  • Number

    • 20% multiple; most common = pineal with suprasellar

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