PNET tumor is highly malignant tumors that affect soft tissues and bones. Majority of the patients that develop this type of malignancy are young children [1, 2].
What is PNET Tumor?
PNET stands for Primitive Neuroectodermal Tumor and pertains to tumors that develop in the brain and spine. This tumor is highly aggressive and commonly develop in the part of the brain that is in control of thought, movement and sensation. The cells that are found in this tumor are immature round cells that are of neuroectodermal origin.
The PNET tumor may look similar to a medullablastoma but tend to form more in the cerebrum and may spread to other parts of the brain. It is usual for the tumor to have areas of necrotic cells and cysts. There are also cases where fluid is found surrounding the tumor. The 5-year survival rate for this type of malignancy is between 50-60% [1, 2, 3]. Figure 2 shows a brain scan of a patient with PNET tumor.
Figure 2 – PNET tumor
Causes and Risk Factors
The rarity of this condition make it hard for researchers to look into the possible causes and risk factors for PNET tumors. Available literature suggests that a genetic predisposition for this malignancy is highly unlikely [4].
PNET Tumor Signs and Symptoms
Signs and symptoms that will present depends on the location of the tumor but some of the common symptoms are associated with the increase in intracranial pressure. These include nausea, headaches, vomiting, lethargy, seizures, alterations in mental status and changes in the behavior of the patient. There may also be unexplained increase or decrease in weight, increasing difficulty in looking upward and weakness on one side of the body [4, 5].
Diagnosis
Health history and physical examination
The focus of the health history is to identify the time when the symptoms have started occurring. The attending physician ma also want to know if these symptoms have increased in intensity and what methods have been effective in relieving symptoms. Physical examination may also include a neurologic examination to identify the extent of the damage to the brain. The neuro exam will assess the reflexes, strength of the muscles, movements of the eye and the mouth and coordination and alertness of the patient [1, 4].
Imaging tests
The use of imaging tests such as CT and MRI can is essential in the diagnosis of PNET tumors. This will not only allow the physician to see the location of the tumor growth but will confirm or rule out metastasis [1, 4].
Cerebrospinal fluid test
A sample of CSF may be collected through a process known as lumbar tap and it will be sent to the laboratory for analysis. The presence of tumor cells in the CSF may indicate that the tumor have spread into the spine [1, 4].
Treatment
Surgery
A surgical removal of the tumor may be performed if there is no metastasis and if no vital structures are affected. If the presence of the tumor lead to the accumulation of fluid in the brain, a physician may prescribe some steroids or may perform a ventriculostomy to reduce the amount of fluid. The reduction in fluid will also lead to a decrease in pressure inside the skull. A shunt may not be advised because of the cases wherein tumor cells have spread to the abdominal cavity because of the presence of the shunt [1, 4, 5].
Chemotherapy
This treatment utilizes antineoplastic drugs to eliminate or inhibit the growth of the tumor. Chemotherapy have improved patient outcomes of PNET. There are several side effects of chemotherapy and the medical team should be able to manage the symptoms or prevent them from occurring. This therapy may also be done in combination with surgery or radiation therapy [1, 4, 5].
Radiotherapy
Radiotherapy utilizes high energy beams such as x-rays to kill tumor cells. This therapy is done in combination with surgery to ensure that no cells remain after the surgery. Although this treatment is effective, it is avoided in patients who are younger than 3 years of age because of the increased likelihood of long-term side effects. These patients may receive chemotherapy until the time radiotherapy will be less dangerous for them [1, 4, 5].
Prognosis
The best outcome for patients with PNET tumors are achieved through radiation. Children below 3 years old have lower survival rate because the use of radiation therapy is avoided. The rate is reduced by about 20-30%. Relapses of PNET tumors are associated with high fatality because there are currently no known effective chemotherapeutic regimen or curative therapy available for this.
References
- Honrado, C. P. (2016, March 1). Primitive Neuroectodermal Tumors . Retrieved from Medscape: http://emedicine.medscape.com/article/855644-overview#a7
- PNET Cancer Foundation. (2013). Primitive Neuroectodermal Tumors of the Central Nervous System (CNS PNET) are identified as highly aggressive large tumors that are found in the brain and spine. Retrieved from PNET Cancer Foundation: http://www.pnetcancerfoundation.com/what-is-pnet.html
- American Brain Tumor Association. (2014). PNET. Retrieved from American Brain Tumor Association: http://www.abta.org/brain-tumor-information/types-of-tumors/pnet.html?referrer=https://www.google.co.nz/
- Dana Farber and Boston Children’s Cancer and Blood Disorders Center. (2015). Primitive Neuroectodermal Tumors (PNET) and Pineoblastoma. Retrieved from Dana Farber and Boston Children’s Cancer and Blood Disorders Center: http://www.danafarberbostonchildrens.org/conditions/brain-tumor/primitive-neuroectodermal-tumors.aspx
- Cancer Research UK. (2016, March 16). Primitive neuroectodermal tumour (PNET). Retrieved from Cancer Research UK: http://www.cancerresearchuk.org/about-cancer/cancers-in-general/cancer-questions/what-is-primitive-neuroectodermal-tumour
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