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Pineocytoma


KEY FACTS

Terminology

  • Pineocytoma (PC), pineal parenchymal tumor (PPT)

  • PCs are composed of small, uniform, mature cells

    • Cells resemble pineocytes

Imaging

  • General features: Circumscribed, enhancing pineal mass

    • May mimic benign pineal cyst or PPT of intermediate differentiation (PPTID)

    • Typically < 3 cm

    • May compress adjacent structures

    • Rarely extends into 3rd ventricle, rarely invasive

    • Can compress aqueduct → hydrocephalus

    • Occasionally hemorrhages

  • CT

    • Circumscribed iso-/hypodense pineal region mass

    • Peripheral (“exploded”) Ca++ common

    • CECT: Enhances (solid, ring, nodular)

  • MR (most sensitive)

    • Cystic change may be present

    • Enhancement may be solid or peripheral

Top Differential Diagnoses

  • Nonneoplastic pineal cyst

  • PPTID

  • Pineoblastoma

  • Germinoma, other germ cell tumors

Clinical Issues

  • Headache, dorsal midbrain (Parinaud) syndrome most common features

  • Increased intracranial pressure, ataxia, hydrocephalus, mental status changes may occur

  • Most common in adults, mean 40 years

  • Stable or slow-growing tumor

  • Germ cell markers (α-fetoprotein, hCG) absent

  • Surgical excision or stereotactic biopsy is primary treatment

    • Complete surgical resection generally curative

Sagittal graphic shows a cystic pineal gland mass
with a fluid-fluid level and nodular tumor along the periphery of the mass, typical of pineocytoma. No significant mass effect is present. Pituicytomas may be found incidentally or present with hydrocephalus.

Axial NECT shows a classic example of a pineocytoma. Note the “exploded” peripheral calcification
in this small mass that arises from the pineal region. The tumor is just over 1 cm in size. There is no hydrocephalus.

Sagittal T1 MR of a 50-year-old woman with headache shows a cystic pineal region mass
with associated ventriculomegaly
and local mass effect on the tectum
. Mass effect on the superior tectum often results in dorsal midbrain (Parinaud) syndrome.

Axial FLAIR MR in the same patient shows the hyperintense, lobular pineal region mass
with associated ventriculomegaly. Pineocytoma was diagnosed at resection. These WHO grade I tumors are often stable for years.

TERMINOLOGY

Abbreviations

  • Pineocytoma (PC)

Definitions

  • Slow-growing pineal parenchymal tumor (PPT) of young adults

    • Composed of small, uniform, mature cells resembling pineocytes

IMAGING

General Features

  • Best diagnostic clue

    • Circumscribed pineal mass that “explodes” pineal calcification peripherally

    • May mimic pineal cyst, pineal parenchymal tumor of intermediate differentiation (PPTID)

  • Location

    • Pineal region

    • Rarely extends into 3rd ventricle

    • Rarely invasive

    • May compress adjacent structures

      • –

        Rarely, associated hydrocephalus if aqueduct compression

  • Size

    • Typically < 3 cm

  • Morphology

    • Demarcated round or lobular mass

CT Findings

  • NECT

    • Iso-/hypodense mass

    • Peripheral (“exploded”) Ca++

    • Cystic change may be present

  • CECT

    • Enhancement present, often heterogeneous

MR Findings

  • T1WI

    • Iso- to hypointense round or lobular mass

  • T2WI

    • Hyperintense round or lobular mass

  • FLAIR

    • Hyperintense round or lobular pineal mass

  • T2* GRE

    • May see Ca++

      • –

        Areas of “blooming” at periphery/within mass

    • May hemorrhage (less common)

  • T1WI C+

    • Avid enhancement is typical

    • Enhancement may be solid or peripheral

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