Primitive neuroectodermal tumor
A primitive neuroectodermal tumor (abbreviation: PNET ; English: primitive neuroectodermal tumor ) is a neural tissue tumor from the group of embryonic tumors. PNET mainly occurs in children and adolescents. A distinction is made between a variant in the central nervous system (brain or spinal cord) and a so-called peripheral variant that occurs outside of it. As malignant tumors, PNETs of the brain are classified as grade IV according to the WHO classification of tumors of the central nervous system .
variants
Central Nervous System PNET (CNS PNET). The first description of a PNET of the central nervous system was in 1973 by Hart and Earle. The subject of their investigations was undifferentiated tumors of the cerebral hemispheres above the roof of the cerebellum (tentorium cerebelli): this observation led to the common name supratentorial PNET (ST-PNET). On a histological basis, the PNET of the central nervous system show clear similarities to medulloblastomas , pineal loblastomas and other types of tumors. Some investigators have taken this similarity as an opportunity to define PNET as a comprehensive group of embryonic tumors of the central nervous system, but this view is controversial.
2.5–6% of all brain tumors in children and adolescents are included in the PNET of the central nervous system. If the medulloblastomas are combined into a group with the PNET (as described above, controversial), this combined group represents 20% of the brain tumors in children and adolescents.
Peripheral PNET (pPNET). Peripheral PNETs are tumors that originate from ectodermally derived body parts. Above all, this includes the autonomic nervous system ( sympathetic and parasympathetic ). Peripheral PNETs typically occur in the area of the chest wall (chest wall): they are then referred to as Askin's tumors . Other locations are also known: kidneys, lungs, uterus, ovaries, testes, pancreas, urinary bladder, parotid glands, skin and subcutaneous fatty tissue have been described as locations in connection with peripheral PNET.
The distinction between peripheral PNET and Ewing sarcoma is not easy: some investigators see Ewing sarcoma as a subgroup of peripheral PNET.
Symptoms
The symptoms are mainly derived from the location (localization) of the PNET. Central nervous system PNETs are noticeable by symptoms such as nausea and vomiting (especially on an empty stomach and in the morning). Loss of skills can also occur (paralysis, visual disturbances, personality changes), which can be explained by neurological failures (loss of nerve functions). Peripheral PNET can initially only be noticed as a swelling, depending on the location. If there is a position inside the body (for example the lungs), difficulty breathing or coughing up blood occurs. Peripheral PNET of the ovaries, pancreas, and uterus are initially noticeable as abdominal pain.
Diagnosis
The trend-setting diagnosis usually takes place via a tissue (histological) examination after sampling (biopsy) or removal of the PNET (resection by surgery). The latter can only be partially or not at all possible, especially with PNET in the central nervous system.
Imaging methods such as ultrasound ( sonography ), computed tomography and magnetic resonance tomography are used before the sampling or operation . What all these methods have in common is that they can provide information about the extent and spread of the PNET. A reliable diagnosis of a PNET using imaging methods alone is not possible.
therapy
First, if possible, surgical removal or at least a sample should be attempted to confirm the diagnosis. This is particularly the case with peripheral PNETs. Following the sampling or operation, polychemotherapy is always carried out in children and adolescents using a combination of various cytostatics . The radiation therapy is used.
For PNETs that are classified as high-risk PNETs or that do not respond adequately to primary treatment, high-dose chemotherapy with subsequent autologous stem cell transplantation is usually carried out.
forecast
The prognosis of PNET varies greatly depending on its location, the operability and the age of the patient. On average for all affected persons, the prognosis of a PNET with a 5-year survival of 53% can be classified as average.
Individual evidence
- ↑ Nicolas R. Smoll: Relative survival of childhood and adult medulloblastomas and primitive neuroectodermal tumors (PNETs) . In: Cancer , Volume 118, No. 5, March 1, 2012, pp. 1313-1322, doi : 10.1002 / cncr.26387 .
