Hello, welcome to the medical advice channel blog, today’s topic is Neoplasia and I hope it will be helpful. Neoplasia is a very broad topic and sometimes thought to be hard to understand, but don’t worry, I will be with you all through the tutorial and try to explain it in the easiest way possible. In this tutorial, we will be discussing the following;
- What is Neoplasia (R.A Willis definition)?
- Limitations of R.A Willis’s definition of Neoplasia.
- Classification of Neoplasia.
- Characteristics and Differences in Benign and Malignant Tumor.
- How malignant tumors spread.
What is Neoplasia?
The word Neoplasia has two parts, Neo which means New, and plasia, which in simple terms means Growth. Now just to be clear, the growth in this case literally means a proliferation of cells or, increase in the number of cells. What we also have to know is that the growth, in this case, is not normal – There is an abnormal growth of the cells. So, how do we define the word Neoplasia? To define Neoplasia, we use the Definition of a famous Oncologist called R.A Willis who developed one of the most important definitions in Pathology. This definition is a must know and a Frequently Asked Question(FAQ) in Pathology.
According to R.A. Willis’ definition, Neoplasia can be defined as An abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of normal tissues, and persists in the same manner even after cessation of the stimuli that evoked the change.
It’s a mouthful, right? don’t worry, I will explain it to you in an easier way. Now, just to clarify, Neoplasia is the actual process, while Neoplasm is the actual term. Therefore, The first point is that Neoplasm is an abnormal mass, and it is uncontrolled, meaning it has a mind of its own, not controlled by the brain or anything(Second Point). Normal cells usually grow in a well-coordinated manner but in Neoplastic cells, this is not the case. The third point is that their growth is persistent unlike in cases like hyperplasia, where when the stimuli are removed, the cells cease from continuing to grow. The above three-point will help you remember the definition of Neoplasm.
Now that you know R.A. Willis’ definition of Neoplasm, let’s look at its limitations.
Limitations of R.A. Willis Definition of Neoplasia.
- We said in the definition that growth of a Neoplastic cell persists, even after we have removed the stimuli, however, this is true not in most cases of Neoplasm, in some cases of Neoplasm, growth can regress in size after the initiating stimuli have been removed. These are mostly Hormone Dependent. Therefore, removing that hormonal stimulation might actually stop the Neoplastic cell’s growth.
- In the definition, we talked about there being a stimulation in order to develop a Neoplasm, but this is not the case in a lot of cases. In most cases, stimulation is not there, or can’t be identified.
These are the two main limitations that examiners always ask about. Moving on, I would like to talk about the term Tumor. We used it earlier to denote swellings, those mainly caused by inflammation. But nowadays, the term Tumor is used interchangeably.
The difference between Hyperplasia and Neoplasia.
You have probably noticed that these two words end with the same prefix, “Plasia’, which means growth, but these are two different terms.
The first difference is that the proliferating cells in Hyperplastic cells are in a normal controlled manner, however, in Neoplastic cells, they proliferate in an uncontrolled and uncoordinated manner.
The second difference is that in Hyperplastic cells, the Proliferation of these cells ceases when the stimuli are removed, unlike in Neoplastic cells where the proliferation does not cease even after cessation of Stimuli.
In the third difference, Hyperplastic cells are usually well-differentiated, differentiation means resemblance to a normal cell. However, in Neoplastic cells, they are not well differentiated and their differentiation usually differs.
Classification of Neoplasm
To understand the naming of Tumors or Neoplastic cells, you first have to know that a tumor has two parts;
- The Parenchyma
- Is made up the Neoplastic cells.
- The Stroma part.
- Is made up of supporting structures mainly connective tissues and blood vessels. Although the parenchyma is the Neoplastic, that is the Neoplastic cells determine the behavior and consequences of a tumor, do remember that the Stroma is also important because it provides the blood supply for that Neoplastic Cell, otherwise the Neoplastic cells cannot grow. Secondly, the Stroma provides a framework on which the Neoplastic cells can grow.
In terms of Naming, we can name tumors according to based on;
Their clinical course.
- Neoplasm or Tumors are also classified as Benign or Malignant tumors.
Always remember that is also called Cancer. They are very stubborn and hard to treat and their growth is very rapid. This is why malignant tumors are given the name Cancer, because of their stubborn nature and invasiveness that continually causes damage. On the other hand, benign tumors are harmless.
Regarding nomenclature, we denote a tumor that is Benign by adding the suffix Oma at the end of the cell of Origin. This rule is more applicable to Benign tumors of Mesenchymal origin, for example;
- Fibroma – It is a benign tumor of Fibroblast.
- Chondroma – Is a benign tumor of the cartilage.
- Osteoma – Is a benign tumor of the Osteoblasts.
Note the Oma suffix at the end which denotes that the tumor is a benign tumor. Now, the above examples apply to those benign tumors of Mesenchymal origin, but when it comes to benign tumors of epithelial origin, it becomes a little bit complicated.
We will use more specific terms to denote the benign tumors of epithelial origin, but in this article, I will mention about four important names that are often used.
This is the first one, where we add the adenoma suffix for tumors of epithelial origin, that are producing a glandular structure or, a benign tumor of glandular origin that may not produce a glandular structure. Confusing right? Let me explain. In the term Adenoma, you notice the ending also has a suffix, Oma, right? this means it is a benign tumor.
Also, notice the Adeno suffix, Adeno means Glands. Therefore, an Adenoma is a benign tumor derived from a gland that may or may not show in glandular structure. Similarly, if a tumor was derived from an epithelial cell or tissue, and that was not originally a gland (It was just an epithelial tissue and not a gland), but is showing a glandular structure, then it will also be considered an Adenoma. Therefore, we can define an adenoma as a benign tumor of glandular origin, that may or may not show glandular structure, as well as a benign tumor of tissue origin.
- If there is a tumor in your adrenal cortex, but that tumor is not producing a glandular structure. Since that tumor was derived from a gland, it is an Adenoma.
- If there is a tumor in your Renal tubules, and that benign tumor is glandular in structure, despite the fact that it is of epithelial origin, it is an Adenoma, because it shows glandular structure.
Papilloma means microscopic finger-like projections beyond the surface.
Is a benign tumor that has a cystic structure.
Is a Macroscopically visible benign tumor. It will have fingerlike projections that are visible microscopically and will project beyond the mucosal surface into the lumen.
Note that there is a malignant form of Polyp known as Polypoid Cancer.
So this is the way we name benign tumors. The main thing is to add the Oma suffix for those of Mesenchymal origin. When it comes to those of epithelial origin, it is a bit complicated because we use oma, Papilloma, cyst, adenoma, polyp, and so on. Important note to remember, not all terms that end with oma, are benign tumors, examples of these terms are;
- Hematoma – Collection of blood in an organ or tissue(often clotted). This is not a Neoplasm but has an Oma.
- Granuloma – Remember inflammation? Then you know this is not a tumor.
When it comes to Malignant tumors, those of Mesenchymal origin can be denoted by adding the word -sarcoma at the end, for example;
- Fibrosarcoma – Is a malignant tumor of the fibroblast.
- Chondrosarcoma – Is a malignant tumor of the cartilage.
For malignant tumors of epithelial origin, we identify them by adding the word -carcinoma at the end. For example;
- Adenocarcinoma – Is a malignant tumor of the adrenal gland.
- Squamous cell carcinoma etc.
There another spatial nomenclature you should know about. These are Mixed tumors and Teratomas.
What are mixed tumors?
Mixed tumors are tumors in which the Neoplastic cells have more than one morphological pattern. An example of this is the Pleomorphic Adenoma of the salivary glands. The salivary glands are the commonest site for pleomorphic adenomas with the parotid gland being the most common of the three salivary glands.
What is Teratoma?
A Teratoma is a tumor derived from more than one germ cell layer. You do remember in your embryology that there are three germ layers;
In the case of Teratomas, the tumor is derived from all three germ layers. Teratomas can often be seen in the Testes, Pineal gland, and in the anterior Mediastinum.
2. Tissue of Origin.
We can also classify Tumors according to their tissue of origin, either as Mesenchymal tumors, epithelial tumors, mixed tumors, etc.
The characteristics and differences between Benign tumors and Malignant tumors
Macroscopic differences between Benign tumors and Malignant Tumors
- Rate of Growth. In Benign tumors, growth is slow while in Malignant tumors, the growth rapid.
- Mode of growth. In benign tumors, the growth is slow, and in an extensive manner while in malignant tumors, the growth is rapid and invasive.
- Capsule. Benign tumors are usually covered by a capsule but there are exceptions and the examiners are very fond of these exceptions, and they may ask you to name the benign tumors that don’t have a capsule surrounding them. These include Leiomyoma of the uterus. On the other hand, malignant tumors don’t have a capsule. they also have exceptions for example renal carcinoma – Malignancy tumor of the renal epithelial cells, which has a pseudo capsule.
Microscopic differences between Benign tumors and Malignant tumors
- Differentiation. This refers to the extent to which a Neoplastic cell resembles a comparable normal cell both morphologically and functionally. Benign tumors are well-differentiated, while in malignant tumors, their differentiation varies. Don’t write that they are poorly differentiated. Remember this because most students get it wrong; Malignant tumors’ differentiation is variable, but most students write that malignant tumors have poor differentiation.
- Anaplasia. Means a lack of differentiation. It is an important feature of malignant tumors. Benign tumors are not anaplastic while malignant tumors are anaplastic. Your examiner may ask what are the evidence that a tumor is malignant? These are anaplasia, invasion, and Metastasis
Feature of Anaplasia
- Pleomorphism. This is variation in size and shape in an anaplastic cell, both in the cytoplasm and the nucleus will display pleomorphism. There will be variation in the size of the cell where it may become too large or too small..
- Nuclear changes in an anaplastic cell. The first thing to occur is that the DNA particles will increase therefore leading to a hyperchromatic nucleus. The second is that the nucleus to cytoplasmic ratio will increase becoming one to one now unlike in a normal cell where the cytoplasm occupies more space, mostly the ratio of 1:4 or 1:6. The third point is that there will be atypical mitosis, the fourth point is that there will be a loss in polarity.
- Invasion. Benign tumors do not invade, while malignant tumors invade the surrounding structures. This is because malignant tumors produce some proteolytic enzymes that can break down the surrounding structures and invade those structures. These structures can be lymphatic’s and veins. Veins are the most common sites of invasion followed by lymphatics, structures like arteries and other structures that contain elastin, collagen and cartilage are more resistant to invasion.
- Metastasis. This is the spread of a tumor from a primary site to a secondary site, which is distant from the site of the primary site of origin. This is the hallmark of malignancy and doesn’t occur in cases of benign tumor
How malignant tumors spread
A malignant tumor can either locally or distally. The local spread occurs via invasion as I mentioned earlier, while the distal spread occurs via metastasis. The different roots of metastasis include;
- Through the natural body passages e.g. Urinary Tract, Gastrointestinal tract.
- Seeding through body cavities e.g. peritoneal cavity, pleural cavity.
- Through Lymphatics. Most carcinomas spread through this route. sarcoma can also spread through this route. can occur through embolic spread or through permeation.
- Though blood vessels, in particular veins. Arteries are more resistant to malignancy due to elastic tissue. Sarcoma usually spread through this route.
Also read: Anemia
Clinical Death Vs Biological death
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