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What is Cancer?

There are many texts and references that attempt to define cancer. The simplest definition is from the American Cancer Society (ACS). According to the ACS, cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells.

Cancer is a result of changes in the body's cells that cause them to grow out of control.

  • A tumor is a mass, or collection, of cells.
  • Tumors can be benign or malignant:
  • Benign tumors are noncancerous.
  • Malignant tumors are cancerous.
  • Metastasis is when malignant tumors travel to areas away from the original or primary site and grow in other different parts of the body

If cancer is not controlled and treated effectively, it can result in death.

Cancer Overview

Cancer, also called malignancy, is an abnormal growth of cells. There are more than 100 types of cancer, including breast cancer, skin cancer, lung cancer, colon cancer, prostate cancer, and lymphoma. Cancer appears in humans of all ages; but, cancers that occur in children below 18 years of age are mainly different than those that occur in adults. Symptoms vary depending on the type. Cancer treatment may include chemotherapy, radiation, and/or surgery.

Site of Cancer Origin

This classification describes the type of tissue in which the cancer cells begin to develop. Here are some common examples of site of origin classification:
  • Adenocarcinoma: originates in glandular tissue
  • Blastoma: originates in embryonic tissue of organs
  • Carcinoma: originates in epithelial tissue (i.e., tissue that lines organs and tubes)
  • Leukemia: originates in tissues that form blood cells
  • Lymphoma: originates in lymphatic tissue
  • Myeloma: originates in bone marrow
  • Sarcoma: originates in connective or supportive tissue (e.g., bone, cartilage, muscle)
  • Mixed Types: These have two or more components of the cancer.

Cancer Diagnosis

A biopsy (removal of tissue for microscopic evaluation) is preferred to establish, or rule out, a diagnosis of cancer.

Usually, a biopsy, along with with advanced imaging technologies, can confirm and locate the presence of cancer in its primary site and secondary sites if metastasized. A cancer's primary site may determine how the tumor will progress; spread, or metastasize; and may also determine related symptoms that are most likely to occur. A secondary site refers to the body part where metastasized cancer cells develop to form secondary tumors.

The pathologist mainly gives a pathological grade to a tumor according to how malignant the tissue looks under the microscope that will finally confirm the presence of cancer. Cancers are additional classified according to stage.

Cancer Staging

Staging is the classification of the extent of the disease of cancer. There are several types of staging methods. We will mainly rely on the below numerical system that will often be used to classify the extent of disease.

Stage 0 Cancer in situ (limited to surface cells)
Stage I Cancer limited to the tissue of origin, evidence of tumor growth
Stage II Limited local spread of cancerous cells
Stage III Extensive local and regional spread
Stage IV Distant metastases


Cancers that Develop in Children

The types of cancers that occur most often in children are different from those seen in adults. The most common cancers of children are:
  • Leukemia
  • Brain and spinal cord tumors
  • Neuroblastoma
  • Wilms tumor
  • Lymphoma (including both Hodgkin and non-Hodgkin)
  • Rhabdomyosarcoma
  • Retinoblastoma
  • Bone cancer (including osteosarcoma and Ewing sarcoma)

Other types of cancers are rare in children, but they do happen occasionally. In very rare cases, children may also develop cancers that are much more common in adults.


Leukemia is cancer of the blood or bone marrow that is responsible of producing blood cells in the human body. A person, who is diagnosed to have leukemia, suffers mainly from an abnormal production of white blood cells, generally referred to as leukocytes. Leukemia is the most common childhood cancers.

Types of leukemia

Chronic and Acute
Leukemia is divided into four large groups. It can be Acute, which is a rapidly progressing disease that results in the accumulation of immature cells in the marrow and blood, or Chronic, which progresses more slowly and allows more mature cells to be produced.

Lymphocytic and Myelogenous
Leukemia is also divided into subcategories according to the type of affected blood cell. If the cancerous alteration occurs in the type of marrow that produces lymphocytes, the disease is called lymphocytic leukemia. A lymphocyte is a kind of white blood cell that is mostly found inside the vertebrae immune system of the body. If the cancerous alteration occurs in the type of marrow cells that go on to produce red blood cells, other types of white cells, and platelets, the disease is called myelogenous leukemia. As a conclusion there are two groups of Leukemia Chronic or acute; Lymphocytic or Myelogenous and therefore we have four main types of leukemia, as illustrated below:
  • Acute Lymphocytic Leukemia (ALL)
  • Chronic Lymphocytic Leukemia (CLL)
  • Acute Myelogenous Leukemia (AML)
  • Chronic Myelogenous Leukemia (CML)

Acute Lymphocytic Leukemia (ALL) and Acute Myelogenous Leukemia (AML) are the most common types of Leukemia in children.

Signs and symptoms:

  • Petechiae: diffuse red to purple spots on the body, caused by a minor hemorrhage due to poor blood clotting as immature white blood cells crowd out blood platelets, which are essential to stop bleeding.
  • Frequent infections: This is due to suppressed white blood cells production responsible for fighting off infection.
  • Anemia: due to the shortage of production of good red blood cells.
  • Dyspnea: labored respiration due to anemia.
  • Pallor: Pale skin color caused by illness.

Other symptoms:
  • Nausea
  • Fever
  • Chills
  • Night sweats
  • Flu-like symptoms
  • Fatigue
  • Weight loss in case the liver or spleen is enlarged this gives a feeling of fullness and decrease in appetite.
  • Headache is more common in cases with the CNS (central nervous system) involvement in cancer.

Treatment of Leukemia:

Leukemia needs to be treated typically with chemotherapy as soon as diseases confirmed. Bone marrow transplant may be considered is some cases.

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