Primitive neuroectodermal tumor

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

Synonyms and keywords: Primitive neuroectodermal tumors; PNET; CNS PNET; Askin tumor; Peripheral neuroepithelioma; Ependymoblastoma

Overview

Primitive neuroectodermal tumor (also known as "PNET") is a rare type of malignant neural crest tumor. PNET arises from the neuroectoderm, which is normally involved in the development of the nervous system. Apart from central nervous system (CNS), PNETs can involve other tissues originating from the neuroectoderm such as muscles and bones. PNET was first discovered by James Ewing, an American pathologist, in 1921. PNETs are more commonly seen among children and young adults . The median age at diagnosis is 25 years of age. Prognosis is generally poor, and the 5-survival rate of patients with PNET is approximately 53%.

Historical Perspective

• Primitive neuroectodermal tumor was first discovered by James Ewing, an American pathologist, in 1921.

Classification

• Primitive neuroectodermal tumor may be classified according to World Health Organization into 3 subtypes:

• Central primitive neuroectodermal tumors (PNETs)
• Neuroblastomas
• Peripheral primitive neuroectodermal tumors (pPNETs)

Pathophysiology

• Primitive neuroectodermal tumor is composed of primitive undifferentiated neuroepithelial cells.
• Primitive neuroectodermal tumors are intracranial and usually located in the cerebral hemisphere.
• The EWS-like gene has been associated with the development of primitive neuroectodermal tumor.
• On gross pathology, characteristic findings of primitive neuroectodermal tumor, include:

• Cystic components

• On microscopic histopathological analysis, characteristic findings of primitive neuroectodermal tumor, include:

• Small blue cell tumor
• Round hyperchromatic cells
• Abundant mitotic figures
• Homer Wright rosettes
• Fibrosis

Causes

• There are no established causes for primitive neuroectodermal tumor.

Differentiating Primitive Neuroectodermal Tumor from Other Diseases

• Primitive neuroectodermal tumor must be differentiated from other diseases that cause seizures, or increase on intracranial pressure, such as:

• Astrocytoma
• Ependymoma
• Oligodendroglioma
• Intracranial teratoma

Epidemiology and Demographics

• The prevalence of primitive neuroectodermal tumor remains unknown.
• Primitive neuroectodermal tumor account for 4-17% of all soft tissue paediatric tumors.

Age

• The median age at diagnosis is 25 years old.
• Primitive neuroectodermal tumor is more commonly observed among children and young adults.

Gender

• Primitive neuroectodermal tumor affects men and women equally.

Race

• There is no racial predilection for primitive neuroectodermal tumor.

Risk Factors

• Common risk factors in the development of primitive neuroectodermal tumor, include:

• Gorlin syndrome
• Turcot syndrome
• Coffin-Siris syndrome
• Cowden syndrome
• Gardner syndrome
• Li-Fraumeni syndrome
• Rubinstein-Taybi syndrome

Natural History, Complications and Prognosis

• The majority of patients with primitive neuroectodermal tumor remain asymptomatic for years.
• Early clinical features are often unspecific.
• If left untreated, patients with primitive neuroectodermal tumor may progress to develop
• Common complications of primitive neuroectodermal tumor, include:

• Increased intracranial pressure
• Cranial nerve palsy
• Seizures

• Prognosis is generally poor, and the 5-survival rate of patients with primitive neuroectodermal tumor is approximately 53%.

Diagnosis

Symptoms

• Clinical presentation of primitive neuroectodermal tumors is often non-specific.
• Symptoms of primitive neuroectodermal tumor may include the following:

• Morning headache
• Restlessness
• Recurrent vomiting
• Diplopia
• Frequent falls
• Positional dizziness

• Obtain medical history, on the following syndromes:

• Gorlin-Goltz syndrome
• Turcot syndrome

Physical Examination

• Patients with primitive neuroectodermal tumor usually are
• Physical examination may be remarkable for:

• Seizures
• Papilledema
• Strabismus
• Nystagmus
• Ataxia
• Motor weakness
• Facial sensory loss
• Third, fourth, and sixth cranial nerve palsies

Laboratory Findings

• There are no specific laboratory findings associated with primitive neuroectodermal tumor.

Imaging Findings

• MRI is the imaging modality of choice for primitive neuroectodermal tumor.
• On CT, findings of primitive neuroectodermal tumor, may include:

• Often seen as a large irregular mass
• Typically iso to hyper-attenuating on non contrast imaging
• Cystic components are common (65%)
• Calcification can be common (70% )
• Shows heterogenous contrast enhancement

• On MRI, findings of primitive neuroectodermal tumor, may include:

• T1: highly variable and can be hypointense to isointense
• T2: generally high signal solid components
• Cystic components are common
• Low signal portions due to calcific components
• T1 C+ (Gd): shows markedly heterogenous enhancement and leptomeningeal seeding is common
• DWI: often shows restricted diffusion
• MR spectroscopy: elevated choline, decreased NAA, elevated taurine (Tau) peak (relatively specific for PNET).

Treatment

Medical Therapy

• There is no treatment for primitive neuroectodermal tumor; the mainstay of therapy is supportive care.

Surgery

• Surgery is the mainstay of therapy for primitive neuroectodermal tumor.

Prevention

• There are no primary preventive measures available for primitive neuroectodermal tumor.