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Pineal Parenchymal Tumor of Intermediate Differentiation (PPTID)


KEY FACTS

Terminology

  • Primary parenchymal neoplasm of pineal gland

    • Intermediate in malignancy between pineoblastoma and pineocytoma

Imaging

  • General features

    • Aggressive-looking pineal mass in adult

    • Extension into adjacent structures (ventricles, thalami) is common

    • Lobulated, moderately vascular

    • Size varies from small (< 1 cm) to large (~ 6 cm)

  • CT

    • Hyperdense mass centered in pineal region

    • Engulfs pineal gland Ca++

    • Hydrocephalus

  • MR

    • T1: Mixed iso-/hypointense mass

    • T2: Isointense with gray matter, + small hyperintense foci

    • FLAIR: Hyperintense

    • Strong, heterogeneous enhancement

    • MRS: Elevated Cho, decreased NAA

  • If aggressive-looking pineal region tumor in middle-aged, older adult, consider PPTID

Top Differential Diagnoses

  • Germinoma

  • Pineocytoma

  • Pineoblastoma

  • Papillary tumor of pineal region

Pathology

  • Neuroepithelial neoplasm

    • Arises from pineocytes or their precursors

  • WHO grade II or III

Clinical Issues

  • Dorsal midbrain (Parinaud) syndrome, headache

    • Upgaze paralysis, convergence-retraction nystagmus

Sagittal T1WI MR in a 21-year-old man with headache shows a pineal region mass
with obstructive hydrocephalus, enlargement of the 3rd ventricle
, and cerebellar tonsillar descent
. Imaging differential considerations include PPTID, pineoblastoma, and germinoma.

Axial T2WI MR shows a very large PPTID
with extension into the ventricular system. Note the heterogeneous T2 appearance of the mass with multiple cystic regions
, typical of PPTID.

(Courtesy L. Loevner, MD.)

Coronal T1WI C+ MR shows a large, peripherally enhancing pineal mass
in a 24-year-old man. PPTID was diagnosed at resection.

MRs in a 48-year-old woman shows elevated choline, decreased NAA, and a lactate doublet. Imaging is too aggressive for a pineocytoma. Germinomas are rare in middle-aged women. Imaging is most suggestive of a PPTID, although a papillary tumor of the pineal region would be a possible diagnosis. PPTID was confirmed at histologic examination.

TERMINOLOGY

Abbreviations

  • Pineal parenchymal tumors (PPT)

  • Pineal parenchymal tumor of intermediate differentiation (PPTID)

Synonyms

  • “Atypical pineocytoma” (old)

Definitions

  • Primary parenchymal neoplasm of pineal gland

    • Intermediate in malignancy between pineocytoma and pineoblastoma

      • –

        Pineocytoma: Slow-growing neoplasm with small mature cells that resemble pineocytes

        • □

          Adults predominate

        • □

          Well-differentiated histology with large “pineocytomatous rosettes”

        • □

          Indolent course (imaging may remain stable for years)

        • □

          Generally good prognosis

      • –

        Pineoblastoma: Highly malignant primitive embryonal tumor of pineal gland

        • □

          Occurs primarily (but not exclusively) in children

        • □

          Poorly differentiated

        • □

          Aggressive behavior

        • □

          Poor prognosis

IMAGING

General Features

  • Best diagnostic clue

    • Aggressive-looking pineal mass in adult

  • Location

    • Pineal gland mass

    • Extension into adjacent structures common: Ventricles, tectum, thalamus

    • CSF dissemination (rare)

  • Size

    • Varies from small (< 1 cm) to ~ 6 cm

  • Morphology

    • Lobulated, moderately vascular

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