Pineocytoma

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Sujit Routray, M.D. [2]

Synonyms and keywords: Pineocytomas; Pinealocytoma; Pinealocytomas; Pineal gland tumor; Brain tumor

Overview

Pineocytoma is a benign, slowly growing pineal parenchymal tumor.

Pathophysiology

Gross Pathology

On gross pathology, pineocytoma is characterized by solid, sometimes with focal areas of cystic change, gray, well-circumscribed mass with or without hemorrhage.

Microscopic Pathology

On microscopic histopathological analysis, pineocytoma is characterized by:

• Cytologically benign cells (uniform size of nuclei, regular nuclear membrane, light chromatin)
• Pineocytomatous/neurocytic rosette, which is an irregular circular/flower-like arrangement of cells with a large meshwork of fibers (neuropil) at the centre

According to the WHO classification of tumors of the central nervous system, pineocytoma is classified into a WHO grade I tumor.

Immunohistochemistry

Pineocytoma is demonstrated by positivity to tumor markers such as:

• Synaptophysin
• Neuron-specific enolase
• GFAP
• Chromogranin A
• PLAP
• Ki-67
• Beta tubulin III

Gallery

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  _{Intermediate magnification micrograph of a pineocytoma. HPS stain.}

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  _{High magnification micrograph of a pineocytoma. HPS stain.}

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  _{Very high magnification micrograph of a pineocytoma. HPS stain.}

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  _{The tumor cells are diffusely positive for synaptophysin and neurofilament.}

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  _{Positivity to Ki-67. The Ki-67 index is 2-3%.}

Differentiating Pineocytoma from other Diseases

Pineocytoma must be differentiated from:

• Pineal parenchymal tumor with intermediate differentiation
• Papillary tumor of the pineal region
• Pineoblastoma
• Pineal germinoma
• Pineal embryonal carcinoma
• Pineal choriocarcinoma
• Pineal yolk sac carcinoma (endodermal sinus tumor)
• Pineal teratoma
• Pineal cyst
• Astrocytoma of the pineal gland
• Meningioma near pineal gland
• Pineal metastasis
• Cavernoma in pineal region
• Aneurysm in pineal region

Epidemiology

Prevalence

• Pineocytoma constitues about 45% of the pineal parenchymal tumors.
• Pineocytoma constitutes about 0.4 - 1% of the intracranial neoplasms.

Age

• Pineocytoma is a rare disease that tends to affect all the age groups, most commonly in the second decade of life.

Gender

• Pineocytoma affects men and women equally.

Natural History, Complication and Prognosis

Natural History

If left untreated, patients with pineocytoma may progress to develop seizures, obstructive hydrocephalus, local recurrence, and CSF metastasis.

Complications

Common complications of pineocytoma include:

• Local recurrence
• CSF metastasis
• Distant metastasis

Prognosis

• Prognosis is generally excellent, and the 5-year survival rate of patients with pineocytoma is approximately 86%.
• Pineocytoma has the most favorable prognosis among all the pineal gland tumors.

History and Symptoms

History

When evaluating a patient for pineocytoma, you should take a detailed history of the presenting symptom (onset, duration, and progression), other associated symptoms, and a thorough family and past medical history review.

Symptoms

• The clinical presentation of pineocytoma is mainly from the obstructive hydrocephalus secondary to compression of the tectum of the midbrain and obstruction of the aqueduct.
• Symptoms of pineocytoma include:

• Headaches
• Nausea
• Vomiting
• Seizures
• Sleepiness
• Irritability
• Personality changes
• Double vision
• Trouble coordinating motor movements
• Difficulty walking
• Slowed growth

Physical Examination

Compression of the superior colliculi can lead to a characteristic gaze palsy, known as Parinaud syndrome. Common physical examination findings of pineocytoma include:

HEENT

• Bulging soft spots (fontanelles)
• Eyes that are constantly looking down (sunsetting sign)
• Deficiency in upward-gaze
• Pupillary light-near dissociation (pupils respond to near stimuli but not light)
• Convergence-retraction nystagmus

Neurological

• Mental retardation
• Muscle spasms
• Loss of bladder control
• Ataxia

CT

• Head CT scan may be diagnostic of pineocytoma.
• Findings on CT scan suggestive of pineocytoma include a mass of intermediate density similar to the adjacent brain with peripheral calcifications.

Gallery

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  _{Different patterns of pineal calcification: Exploded calcification of tumors of pineal cell origin and engulfed calcification by germinomas.}

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  _{Single image following biopsy and third ventriculostomy demonstrates a pineal region soft tissue mass. A small amount of blood is seen in the occipital horn on the right. Ventricles remain dilated.}

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  _{A 14 X 13 mm (axial) soft tissue density mass in the pineal region with eccentric peripheral calcification demonstrated. The ventricles are prominent, out of keeping with the degree of sulcal prominence, indicating mild to moderate obstructive hydrocephalus due to the lesion partially obstructing the upper margin of the cerebral aqueduct. Periventricular hypoattenuation is in keeping with chronic small vessel ischaemia +/- transependymal CSF accumulation.}

MRI

• Brain MRI may be diagnostic of pineocytoma.
• Features on MRI suggestive of pineocytoma include:

MRI component	Findings
T1	Isointense to brain parenchyma
T2	Solid components are isointense to brain parenchyma Areas of cystic change Sometimes the majority of the tumor is cystic
T1 with gadolinium contrast	Solid components vividly enhance

Gallery

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  _{A large and ill-defined mass is present in the region of the pineal gland, demonstrating contrast enhancement.}

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  _{Axial T2 demonstrating a circular mass centered in pineal region measures 12 x 11 x 9 mm and demonstrates homogeneous enhancement (on volumetric sequence for stereotaxis), peripheral calcification, and diffusion restriction. It has mass effect on the adjacent structures with stenosis of the cerebral aqueduct (some flow still present on cine imaging) and associated non-communicating hydrocephalus affecting the lateral ventricles and 3rd ventricle. Foramina of Monroe are patent. No other suspicious enhancing lesion, including of the leptomeninges. No suprasellar/sellar mass in non-dedicated study.}

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  _{T2 MRI image demonstrating a well circumscribed mass is located in the region of the pineal gland. It is a little heterogeneous with multiple small regions of cyst formation (on T2) most marked anteriorly, probably at the site of biopsy.}

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  _{Axial T1 with contrast demonstrating a large enhancing mass is present in the pineal region compressing the tectum and resulting in obstructive hydrocephalus.}

Treatment

The mainstay of therapy for pineocytoma is surgery (gross total or subtotal resection).

References

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