NEURONAL CELL TUMORS

This course was a very useful tool as a review of neurophysiolgy. I wish that my teachers would have explained these complex processes as clear as I saw them in this course.

These classes also awoke my curiosity about neuronal neoplasms. During the course we were told that there are not neuronal tumors, but in the laboratory there are reported cases of neuronal neoplasms. Some characteristics that they display have convinced some of us that they are really of neuronal nature.

I chose this topic because I think that it can be an interesting and controversial issue for us all, and we all can discuss and learn a lot one from the others. I will wait your comments and new information that you would like to add to this little discussion.

Before we start with the main issue of this final project, I only want to make a quick review of the principal cells of the central nervous system: The neurons an the glia.

The neuron is the functional unit of the nervous system. It’s an electrically, excitable cell that transmits information through electrical and chemical signs in the central and peripheral nervous system. They allow us to think, to use our five senses, to move, etc.

And as for the glial cells, they are more numerous than neurons. They retain the capacity to proliferate. They mantain the brain homeostasis, form myelin and provide support and protection for the neurons.

With this information in mind, now we will make a rapid review of the structure of a neuron. Neurons have typically a soma or cell body, with multiple projections from the soma that consitute the dendrites, where the information is received, and a long axon, that ends up in the synaptic terminal. The axon transmits the impulse outside of the neuron.

As all the cells of the body, the neurons have inside of them a nucleus as well other organelles, like reticulum endoplasmic, mitochondria and golgi apparatus.

But every cell of the body has some particular features that allow them to function properly in the organ where they are placed. We can identify these specialized structures in order to establish the nature of the cell.

Every cell of the body needs filaments, some long proteins that allow them to keep their shape and provide structural support. In the case of neurons, these filaments are of a specialized type and called neurofilaments. They also help in the axonal transport. In this image the neurofilaments are colored in green.

Neuronal cells also express synaptophysin, a glycoprotein that is present in the vesicles of the synaptic terminal.

Using different methods in the laboratory, we can establish the origin of a neoplasm. Most of the neoplasms of the central nervous system arise from the glia, but a few of them seem to arise from neuronal cells.

The neuronal cell tumors, also called ganglionar cell tumors, use to come to neurosurgical intervention within the three decades of life. Commonly they are localized in the supratentorial area.

Although defined by its neuronal component, some of them are mixed with glial elemements, and are consequently called gangliogliomas. Those composed purely of neuronal cells are called gangliocytomas.

In the neuronal neoplasms, the ganglion cells elabortae cytoplasmic processess with the argyrophilia typical of axons on neurohistochemical study, and also contain parallel microtubular arrays and clear presynaptic-type vesicles on utrastuctural examination.

Although some tumors of glial lineage sometimes asume neuronal cells appearance, they manifest none of these specialized features, characteristic of neuronal cells.

Another important clue is to observe the neoplastic alterations in the neuronal cells, for example gigantism, pleomorphism and multinucleation. These make the difference with the glial tunors that only have trapped neuronal cells.

I will discuss only one example of these rare neoplasms: The Central Neurocytoma

The Central Neurocytoma is a rare tumor that usually is located in the intraventicular system, usually blocking the foramen of Monro. and for the same reason produces symptoms and signs of increased intracranial pressure. It appears in young adults

In the MRI image we can aprecciate its intraventricular location. The microscopic image shows up some round cells embedded in a delicate fibrillar matrix

This tumor is not agressive. Only needs surgical resection. It is believed that it has a neuronal origin because it expresses synaptophysin, and neurofilaments in the immunohistochemistry studies, and neuritic processes replete with microtubules and synsaptic-type vesicles in the electron mycroscopy.

In this image we can appreciate the highly positive result for synaptophysin. An antibody was used to target the synaptophysin proteins that display a strong golden brown color.

The findings in electron microscopy show up clear synaptic vesicles.

All these findings led some of us to believe in a neuronal origin. It’s weird, because we know that neuron cells do not divide after birth, but medicine is not an exact science like mathematics. I’m looking forward for your comments.

I also give thanks for this awesome course, and I specially give thanks to God for all the marvelous things that He prepared for us when He designed our body.

Ackerman’s Surgical pathology, Juan Rosai 8th. Edition, pages 2303-2308

Histology and Cell Biology, an Introduction to Pathology, Kierszenbaum, 3th edition, pages 229-234

BIBLIOGRAPHY

THANKS