Anaplasia Definition

Anaplasia is a term used to describe cells that have lost the unique characteristics that define them as a certain tissue type. In a literal sense from its Greek roots, the word means “to form backwards” in the sense that normal cells become more specialized, not less so, with each division. Anaplasia can be explained as when a cell ‘reverts’ to a more stem-cell like state, one that is often distorted. Often seen in cancer cells, the cell no longer functions as part of the tissue that surrounds it. As the cell undergoes mitosis, it produces cells that also display anaplasia. In this way, a malignant tumor is born.

In normal cells, growth stops when a neighbor is reached. Normal cells communicate with each other to provide the proper shape for tissues. Without this communication, each cell in a tumor showing anaplasia will grow to be much bigger than a normal cell, and will be only very loosely connected to the cells around it. Without the ability to form bonds to the cells around them, malignant tumors can metastasize, or get loose and travel through the blood stream to other parts of the body. This can become an extremely dangerous situation, as the newly colonized tumors will start to grow quickly. If the tumor’s new home is a place in your body that is important for living, like inside your brain, it can quickly kill you. This lack of differentiation, or anaplasia, is often what determines whether a tumor is malignant or benign.

Tumors that show increased mitosis, but are still differentiated into the right kind of tissue, are often benign. It is much harder for cells to metastasize if they are still strongly bound to the other cells around them. In the case of a benign tumor, the cells are simply replicating too fast, and cause a mass to form. Often, these can be removed with surgery without the risk of any spread. Malignant tumors with anaplasia are often treated with radiation and chemotherapy after surgery to kill any small tumors that have metastasized to other parts of the body.

Cells, or groups of cells displaying anaplasia will often have similar symptoms. They get much larger than the cells around them, and start dividing in unequal, often curious, ways. Instead of an equal split of cell contents during mitosis, strange phenomena cause the size and shapes of the cells to be unequal. The nucleus tends to get much larger, proportionally, to the size of the cytoplasm, than in a normal cell. Some cells with anaplasia will have multiple nuclei. Inside the nuclei, the bound-up DNA, or chromatin, takes on a course appearance. Cells with anaplasia will lose their functionality as well, making them ‘stem-cell’ like. For instance, a mucus secretion cell will no longer secrete mucus, and will just exist to go through mitosis.

Examples of Anaplasia

Leiomyosarcoma vs Leiomyoma

The difference that anaplasia can make is astonishing. Anaplasia gives cancers a very unpredictable nature, making them hard to treat with chemotherapy and radiation. This can be seen in the two cancers Leiomyosarcoma (a malignant smooth muscle tumor) and Leiomyoma (a benign smooth muscle tumor). The only difference between the two cancers is the state of anaplasia that exists in the malignant form.

The lack of differentiation causes the cancerous cells to do crazy things, like rapidly divide and then go dormant for a period of time. It is not yet known exactly what causes the change in a cell for it to become anaplastic. While malignant tumors don’t have to display anaplasia to be malignant, much as in the case of these two cancers, anaplasia can turn a benign tumor into a malignant one.

Adenoma to Adenocarcinoma

Another example which shows how anaplasia can make a cancer malignant can be seen in the following example. In some adenomas (benign glandular tumors), a change can cause the cells to become less differentiated, or to show anaplasia. In this case, these benign cells can actually become a malignant adenocarcinoma. Most often, they do not.

Again, it is important to recognize that this is only one possible outcome of an adenoma. Most will stay benign. However, other mutations can cause an adenocarcinoma to occur without a benign tumor developing first. Just because one can come from the other does not make this the only way to develop a malignant tumor.

  • Metastasize – When cancerous cells break off the tumor they originated from, travel through the body using the blood stream, and arrive at a new location, they are able to colonize a new tumor.
  • Differentiate – The ability of a cell to specialize in function to perform a very narrow set of tasks for the body.
  • Carcinoma – Any cancer that forms from the epithelial surfaces, which include your skin and the linings of all internal ducts, tracts, and organs.
  • Sarcoma – Any cancer that forms from connective tissues such as smooth muscle, bone, and cartilage.


1. Hello, Doctor. A new type of cancer has been found in one of your patients. It appears that the tumor shows signs of anaplasia; how should we proceed?
A. Cut it out.
B. Sugar pills. See if the placebo effect works.
C. After surgery, give chemo and radiation.
D. None of the above.

Answer to Question #1
C is correct. Anaplasia in a tumor can mean that the cells are not communicating and attaching to each other like they are supposed to. This can lead to metastasis, which could be very dangerous. Most malignant cancers must be treated with chemotherapy and radiation to kill the remaining cancer cells. Chemotherapy and radiation work by targeting cells which are actively dividing, in the hope that the cancer is still actively dividing. However, some cancers can lay dormant, and won’t be dividing during the treatment. Those cancers will not be affected, and may become active again in the future.

2. You’re looking at a tissue sample from a patient who has a tumor. You are trying to determine whether it is malignant or benign. The cells appear to still be specialized, and the nuclei are intact, but they are reproducing at a higher rate than normal tissue of that type. What conclusion do you draw?
A. The cells are probably malignant.
B. The cells are probably benign.
C. The cells are just better at mitosis than normal cells.
D. None of the above.

Answer to Question #2
B is correct. The cells, while cancerous, have a low likelihood of metastasizing if they are still functioning and communicating with the cells around them. With the nuclei still the same size and intact, no anaplasia appears to be happening. While there is still a chance that these cells are malignant if they reproduce too quickly or start to obstruct pathways, it is likely these cells are benign and can be removed in surgery.

3. You are looking at a sample of tissue from a patient’s skin. In the sample, there are cancerous cells that appear to display the symptoms of anaplasia. However, the cells displaying anaplasia appear to be muscle cells. These muscle cells must have metastasized from a tumor in the smooth muscle. What do you call this cancer?
A. Sarcoma
B. Carcinoma
C. Mesothelioma
D. None of the above.

Answer to Question #3
A is correct. Because the cells originated in the smooth muscle, or connective tissue, the cancer is a sarcoma. Had the cancerous cells come from the skin, the cancer would be a carcinoma, even if the tumor was found in the muscle. In this way, it is more important where the cancer came from than where it is now. However, because the sarcoma is found in the skin, we know that the cancer has metastasized, and to treat it we must use aggressive chemotherapy and radiation.