Pineal Gland Tumors - Complete Clinical Review

Classification

Clinical Features

1. Raised Intracranial Pressure (most common presentation)

• Headache (often severe)
• Nausea and vomiting
• Papilloedema
• The tumor compresses the cerebral aqueduct (Sylvius), causing obstructive hydrocephalus

2. Parinaud's Syndrome (dorsal midbrain syndrome) - pathognomonic

• Loss of upward gaze (most characteristic)
• Loss of convergence
• Pupils: large, react to accommodation but NOT to light (light-near dissociation)
• Retractatory nystagmus on attempted upgaze
• Convergence-retraction nystagmus

3. Endocrine Features

• Precocious puberty in males with germinomas (HCG secretion stimulates Leydig cells)
• Diabetes insipidus if hypothalamus involved
• Sleep disturbance (melatonin disruption, though usually mild)

4. Pineal Apoplexy (rare)

• Sudden hemorrhage into the tumor
• Presents with sudden severe headache + depressed consciousness - mimics subarachnoid hemorrhage
• CT/MRI distinguishes it

5. Late/Additional Features

• Cerebellar ataxia (compression of superior cerebellar surface)
• Spastic weakness
• Diplopia (CN VI or III compression)
• Seizures (uncommon)

Histopathology (H&E)

• Pineocytoma: Lobular architecture, pineocytomatous rosettes (tumor cells around acellular neuropil center), rare mitoses, synaptophysin+
• PPTID: Sheets of cells, minimal pleomorphism, rosettes absent or rare
• Pineoblastoma: Dense cellularity, nuclear molding, numerous mitoses, necrosis, apoptotic bodies - resembles medulloblastoma; DROSHA mutations common
• Germinoma: Large spherical epithelial cells with reticular connective tissue + many lymphocytes
• PTPR: Papillary architecture with cuboidal/columnar cells on fibrovascular cores; keratin+ and S100+; PTEN mutations, loss of chromosome 10

Investigations

Neuroimaging (primary investigation)

• MRI brain with contrast - investigation of choice
  • Shows tumor, compresses tectum and aqueduct
  • T2-FLAIR: shows hydrocephalus and transependymal CSF flow
  • Sagittal view best for demonstrating tectal compression
• CT head - initial; detects calcification (pineal calcification displaced/enlarged), hemorrhage

Tumour Markers (serum AND CSF)

• Typical germinomas show little elevation of either AFP or β-hCG; significant elevations suggest complex mixed germ cell tumors.

CSF Analysis

• Lumbar puncture (after safe imaging - exclude raised ICP)
• May show tumor cells, lymphocytes, or be entirely normal
• Cytology important for staging (neuraxis seeding)

Histopathology / Biopsy

• Stereotactic biopsy or open surgical biopsy
• Required because each tumor type requires different management
• Endoscopic biopsy via ETV (endoscopic third ventriculostomy) is common in pediatric practice

Management

Step 1 - Treat Hydrocephalus

• External ventricular drain (EVD) - emergency
• Endoscopic Third Ventriculostomy (ETV) - preferred definitive treatment for hydrocephalus; can be combined with biopsy
• VP shunt (if ETV not feasible)

Step 2 - Histological Diagnosis

• Supracerebellar infratentorial approach - most common
• Occipital transtentorial approach
• Occasionally, if markers are diagnostic (high AFP or β-hCG), empirical treatment may be initiated

Step 3 - Tumor-Specific Treatment

• Germinoma: >90% 5-year survival with RT
• Pineocytoma: excellent after resection
• Pineoblastoma: poor despite combined therapy

Differential Diagnosis

Key Points Summary

• The pineal gland lies in the epithalamus overlying the pretectal area and rostral midbrain, technically outside the brain parenchyma.
• Germinoma is the most common pineal region tumor (~50%); highly radiosensitive with excellent prognosis.
• The classic triad is: raised ICP + Parinaud syndrome + endocrine disturbance.
• Pineal parenchymal tumors express synaptophysin; DROSHA mutations are common in pineoblastoma.
• All pineal tumors should be biopsied/resected when feasible because management differs dramatically by histotype.
• MRI with gadolinium is the cornerstone imaging tool.