Pineal Mass

Bernadette L. Koch, MD

DIFFERENTIAL DIAGNOSIS

Common

Pineal Cyst

Less Common

Germinoma
Teratoma

Rare but Important

Pineoblastoma
Retinoblastoma
Pineocytoma

ESSENTIAL INFORMATION

Helpful Clues for Common Diagnoses

Pineal Cyst
- Key facts
  - Intrapineal glial-lined cyst, nonneoplastic
  - May form or involute over time
  - Majority 5-10 mm and asymptomatic; may be > 20 mm
  - Rarely hemorrhage, acute hydrocephalus, or Parinaud syndrome
  - Incidence of cysts > 5 mm: 11-20 years (3%), 21-30 years (3.4%), 70 years (< 0.5%)
  - If > 1 cm, nodularity, or associated clinical symptoms, recommend short interval follow-up
- Imaging
  - Well-defined, uni-/multiloculated cyst
  - Posterior to 3rd ventricle, above tectum, below internal cerebral veins
  - If large, may flattening of tectum, aqueduct compression, internal cerebral vein elevation
  - T1 and T2WI; Iso- to hyperintense to CSF
  - FLAIR: Usually hyperintense to CSF
  - DWI: Typically isointense to CSF
  - T2* GRE: Occasionally bloom if recent or old hemorrhage
  - ± thin (< 2 mm) rim of enhancement = compressed pineal tissue
  - Rarely nodular enhancement
  - Avoid delayed post-contrast imaging; may show enhancement of cyst contents, making differentiation from tumors impossible

Helpful Clues for Less Common Diagnoses

Germinoma
- Key facts
  - Tumor of primordial germ cells
  - Most common pineal tumor in children
  - 30-40% of CNS germinomas in pineal region (50-60% suprasellar, up to 14% thalamus and basal ganglia)
  - Males > > females in pineal region
  - Males ≈ females in suprasellar region
  - Present with headache, hydrocephalus, and Parinaud syndrome (paralysis of upward gaze)
- Imaging
  - Classic well-defined mass “engulfs” pineal gland
  - CT: Iso-/hyperdense to gray matter
  - T1 and T2WI: Iso- to hypointense relative to GM
  - ± hyperintense cysts T2WI
  - FLAIR: Iso- to hypointense relative to gray matter
  - DWI: Restricted diffusion
  - Avid contrast enhancement; “speckled” enhancement common
  - Relatively small lesion may ventricular obstruction
  - May engulf or displace pineal Ca++
  - MRS: ↑ choline, ↓ NAA, ± lactate
  - ± enhancing subarachnoid metastases
Teratoma
- Key facts
  - 2nd most common pineal tumor in children
  - Benign, nongerminomatous germ cell tumor
  - Mature, immature, and malignant types
  - Males > > females pineal and suprasellar region
  - Present with headache, hydrocephalus, and Parinaud syndrome (paralysis of upward gaze)
- Imaging
  - Heterogeneous pineal region mass with fat, soft tissue, Ca++, and cysts
  - T1WI: ↑ signal from fat, variable signal from Ca++
  - T2WI: Soft tissue iso- to hyperintense
  - FLAIR: ↓ signal intensity from cysts, ↑ signal intensity from solid tissue
  - MRS: ↑ lipid moieties on short echo
  - Fat suppression MR helps to confirm fat content
  - Difficult to distinguish mature from immature by imaging
Pineoblastoma
- Key facts
  - Primitive neuroectodermal tumor (PNET) of pineal gland
  - Highly malignant
  - Children > adults
  - Up to 40% in infants
- Imaging
  - Large (usually > 3 cm) pineal mass
  - Hydrocephalus 2° aqueductal obstruction
  - “Exploded” peripheral Ca++ on CT
  - Extension into 3rd ventricle, thalamus, midbrain, cerebellar vermis common
  - CT: Solid portion hyperdense
  - T1WI: Solid portion iso- to hyperintense relative to GM
  - T2WI: Solid portion iso- to hyperintense relative to GM; mild peritumoral edema common; frequent necrosis; occasional hemorrhage
  - Moderate heterogeneous enhancement
  - MRS: ↑ choline, ↓ NAA
  - CSF spread in up to 40% at time of presentation