Pineal yolk sac tumor
Synonyms and keywords: Pineal yolk sac tumors; Pineal yolk sac tumour; Pineal yolk sac tumours; Pineal endodermal sinus tumor; Pineal endodermal sinus tumors; Pineal endodermal sinus tumour; Pineal endodermal sinus tumours; Pineal yolk sac carcinoma; Pineal yolk sac carcinomas; Pineal gland tumor; Germ cell tumor; Brain tumor

# Overview
Pineal yolk sac tumor is a rare type of extra gonadal yolk sac tumor. They make up a small fraction of all intracranial germ cell tumors and an even small fraction of pineal masses overall.Pure pineal yolk sac tumors secrete AFP.On microscopic histopathological analysis, pineal yolk sac tumor is characterized by poorly differentiated endothelial-like, cuboidal, or columnar cells with prominent nucleoli and significant mitotic activity.Pineal yolk sac tumor is demonstrated by positivity to tumor markers such as AFP, cytokeratin, and AAT.In upto 50% of cases, these tumors co-exist with other germ cell tumors
Pineal yolk sac tumor may be associated with Down syndrome.Common complication of pineal yolk sac tumor includes obstructive hydrocephalus.Prognosis of pineal yolk sac tumor is generally poor.Symptoms of pineal yolk sac tumor include headache, nausea, vomiting, weakness, confusion, and somnolence.Head CT scan and brain MRI may be helpful in the diagnosis of pineal yolk sac tumor.On head CT scan, pineal yolk sac tumor is characterized by a hypodense, heterogenous mass in the pineal region with signs of obstructive hydrocephalus.On brain MRI, pineal yolk sac tumor is characterized by hypointensity on T1-weighted images and hyperintensity on T2-weighted images.There may be enhancement after contrast administration.Biopsy is generally done to confirm the diagnosis of pineal yolk sac tumor.

# Historical Perspective
- Tumors of brainstaim as well as pineal gland,were unoperable until late of 20th century.
- Dr Cushing reported one of the first case in 1904.
- Dr Horsley in 1905 was the first who did direct surgical intervention,and in 1913 Dr Oppenhein and Krause resected pineal tumor sucssesfully.
- There are only two case Reports of pineal yolk sac tumor that are associated with Down's syndrome in English literature.

# Classification
- There is so many classification system for pure pineal tumors.
- The most current system is for World Health Organization(WHO).
- Louis and associates edited classification of Central Nervous System tumors  and published in 2007.
Adapted from WHO:

# Pathophysiology
- The exact pathogenesis of extragonadal germ cell tumors is not fully understood.
- It is thought that extragonadal germ cell tumors  is the result of arresting erroneously of precursos germ cells in midline migration during emberiogenesis.
- The other theory is that EGGCTs are metastases of undiagnosed primary GCTs. 

# Causes
- The intracranial GCTs are resulting of many mutations of MAPK/PI3K/mTOR pathway.

# Differentiating Intracranial Germ cell Tumors from Other Diseases
- Intracranial germcell tumors must be differentiated from other diseases that cause compressive syndrome ,rise of intracranial pressure , such as other brain tumors and every disease who can rise ICP.
- Extra gonadal Germ cell tumors should be in differential diagnosis of pineal germ cell tumors.

# Epidemiology and Demographics
- The incidence of pineal tumor is approximately  of all intracranial tumors.
- The incidence of pineal tumor is 0,06 -0,07 per 100,000 persons per year.
- Patients of all age groups may develop pineal yolk sac tumor,But is more common in children(3-8%)and also in   Japenes population.
- There is no racial predilection to pineal tumors.
- pineal tumors affect men more than women.
- The majority of pineal tumor cases are reported in Japenes population.

# Risk Factors
- There are no established risk factors for pineal yolk sac tumor.

# Screening
- There is insufficient evidence to recommend routine screening for pineal yolk sac tumors.

# =Natural History, Complications, and Prognosis
- The 5 year survival rate of patients with intracranial germ cell tumors is approximately 80%.
- We can classified intracranial germ cell tumors to three main groups;  good,intermediate and bad.
- pineal yolk sac tumor is in the poor prognosis classification.
- Factors that make poor prognosis is ;female ,age greater than 18,non germinoma GCTs.

# Diagnosis

## Diagnostic Study of Choice
- In 54% of cases diagnosis is delayed because of non-specific symptoms.
- The diagnosis of cranial germ cell tumors is based on the CT,MRI with gadolinium fundings and level of biomarkers(HCG,AFP)of serum and csf.also histology need for diffrentiate type of GCTs.With normal biomarkers level ,for definitive diagnosis biopsy is requiered.
- In addition we should determine Immunohistochemichal markers for diagnosis(c-kit/CD117,oct3/4,PLAP).

# =History and Symptoms
- The most common symptoms of intracranial germ cell tumors include parinaud syn (because of hydrocephalus or commpresion of tectal plate ). Common symptoms of intracranial GCTs include DI(due to hydrocephalus), ataxia and dysmetria if affecting superior cerebellar peduncles, precocious puberty,headache ,nausea,ocolomotor or facial paresis,seizure.

## Physical Examination
- Common physical examination findings of intracranial GTCs include papillary edema,gate disturbance,
facial nerve parasia.

## Laboratory Findings
- An elevated concentration of serum/CSF HCG,AFP is diagnostic of Germ cell tumors.

## Electrocardiogram
- There are no ECG findings associated with intracranial GCTs.

## X-ray
- There are no x-ray findings associated with pineal yolk sac tumors.

## Echocardiography or Ultrasound
- There are no echocardiography/ultrasound  findings associated with Pineal yolk sac tumors.

## CT scan
- Brain CT scan may be helpful in the diagnosis of intracranial Germ cell tumors. Findings on CT scan suggestive of cranial yolk sac tumors include irregular mass,may have multi cysts, and solid component has calcifications,also in plain CT is iso-low density mass with heterogenous enhancement.

# =MRI
- Brain MRIT2-based may be helpful in the diagnosis of cranial germ celltumors. Findings on MRI T2 based diagnostic of intracranial GCTs include hyperintense to normal paranchyma.

## Other Imaging Findings
- There are no other imaging findings associated with cranial GCTs.

# =Other Diagnostic Studies
- Immunohistochemichal markers and histological features may be helpful in the diagnosis of cranial GCTs. Findings suggestive of yolk sac tumor include reticular /microcytic,psudopapillary/endodermal sinus,glandular and solid patterns.

# Treatment
- The mainstay of therapy for pineal yolk sac tumor is radiotherapy and/or chemotherapy. Sometimes, surgical resection may be done.