Cancer Classification

Dr. Merdiye Mavis

• A tumor can be either benign or malignant.
• Benign tumor: A tumor that remains confined to its original location,
neither invading surrounding normal tissue nor spreading to distant
body sites.
• For examples; Skin wart
• Malignant tumor: A tumor which is capable of both invading
surrounding normal tissue and spreading (metastasis) throughout the
body via the circulatory or lymphatic systems.
• Only malignant tumors are properly referred to as cancer.
Cancer Classification
• Cancers are classified in two ways:
• by the type of tissue in which the cancer originates (histological type)
• by primary site, or the location in the body where the cancer first developed.
Cancer classification based on histological type
• From a histological standpoint there are hundreds of different
cancers, which are grouped into six major categories:
• Carcinoma
• Sarcoma
• Myeloma
• Leukemia
• Lymphoma
• Mixed Types
Carcinoma
• Carcinoma refers to a malignant neoplasm of epithelial origin or
cancer of the internal or external lining of the body.
• Carcinomas account for 80 to 90 % of all cancer cases.
• Carcinomas are divided into two major subtypes:
• adenocarcinoma, which develops in an organ or gland
• squamous cell carcinoma, which originates in the squamous epithelium.
• Adenocarcinomas generally occur
in mucus membranes.
• First seen as a thickened plaque-like
white mucosa.
• They often spread easily through
the soft tissue where they occur.
• Squamous cell carcinomas occur in
many areas of the body.
• Most carcinomas affect organs or
glands capable of secretion, such as
the breasts, which produce milk, or
the lungs, which secrete mucus,
or colon or prostate or bladder.
Sarcoma
• Sarcoma refers to cancer that originates in supportive and connective
tissues such as bones, tendons, cartilage, muscle, and fat.
• Generally occurring in young adults, the most common sarcoma often
develops as a painful mass on the bone.
• Sarcoma tumors usually resemble the tissue in which they grow.
Examples of sarcomas are:
• Osteosarcoma or osteogenic sarcoma (bone)
• Chondrosarcoma (cartilage)
• Leiomyosarcoma (smooth muscle)
• Rhabdomyosarcoma (skeletal muscle)
• Mesothelial sarcoma or mesothelioma (membranous lining of body
cavities)
• Fibrosarcoma (fibrous tissue)
• Angiosarcoma or hemangioendothelioma (blood vessels)
• Liposarcoma (adipose tissue)
• Glioma or astrocytoma (neurogenic connective tissue found in the brain)
• Myxosarcoma (primitive embryonic connective tissue)
• Mesenchymous or mixed mesodermal tumor (mixed connective tissue
types)
Myeloma
• Myeloma is cancer that originates in
the plasma cells of bone marrow.
• The plasma cells produce some of the
proteins found in blood.
Leukemia
• Leukemias ("liquid cancers" or "blood cancers") are cancers of the
bone marrow
• The word leukemia means "white blood" in Greek.
• The disease is often associated with the overproduction of immature
white blood cells.
• These immature white blood cells do not perform as well as they
should, therefore the patient is often prone to infection.
• Leukemia also affects red blood cells and can cause poor blood
clotting and fatigue due to anemia.
Examples of leukemia include:
• Myelogenous or granulocytic leukemia (malignancy of the myeloid
and granulocytic white blood cell series)
• Lymphatic, lymphocytic, or lymphoblastic leukemia (malignancy of
the lymphoid and lymphocytic blood cell series)
• Polycythemia vera or erythremia (malignancy of various blood cell
products, but with red cells predominating)
Lymphoma
• Lymphomas develop in the glands or nodes of the lymphatic system,
a network of vessels, nodes, and organs (specifically the spleen,
tonsils, and thymus) that purify bodily fluids and produce infection-
fighting white blood cells, or lymphocytes.
• Unlike the leukemias which are sometimes called "liquid cancers,"
lymphomas are "solid cancers."
• Lymphomas may also occur in specific organs such as
the stomach, breast or brain.
• These lymphomas are referred to as extranodal lymphomas.
• The lymphomas are subclassified into two categories:
• Hodgkin lymphoma and Non-Hodgkin lymphoma.
• The presence of Reed-Sternberg cells in
Hodgkin lymphoma diagnostically distinguishes Hodgkin lymphoma
from Non-Hodgkin lymphoma.
Mixed Types
• The type components may be within one category or from different
categories. Some examples are:
• adenosquamous carcinoma
• mixed mesodermal tumor
• carcinosarcoma
• teratocarcinoma
Cancer staging
• Staging is a way of describing the size of a cancer and how far it has
grown. When doctors first diagnose a cancer, they carry out tests to:
• check how big the cancer is
• whether it has spread into surrounding tissues
• whether it has spread to other parts of the body

• Types of staging systems

• There are 2 main types of staging systems for cancer. These are the TNM
system and the number system.
TNM Staging
• The TNM staging system stands for Tumour, Node, Metastasis.
• T describes the size of the tumour
• N describes whether there are any cancer cells in the lymph nodes
• M describes whether the cancer has spread to a different part of the
body
• The system uses letters and numbers to describe the cancer.
• T refers to the size of the cancer and how far it has spread into nearby
tissue. It can be 1, 2, 3 or 4, with 1 being small and 4 large.
• N refers to whether the cancer has spread to the lymph nodes. It can
be between 0 and 3. 0 means that there are no lymph nodes
containing cancer cells. And 3 means that there are lots of lymph
nodes containing cancer cells.
• M refers to whether the cancer has spread to another part of the
body. It can either be 0 or 1. M0 means that the cancer hasn't spread
and M1 that the cancer has spread.
Number staging systems
• Number staging systems use the TNM system to divide cancers into stages. Most
types of cancer have 4 stages, numbered from 1 to 4.
• Stage 1 usually means that a cancer is small and contained within the organ it
started in
• Stage 2 usually means that the tumour is larger than in stage 1 but the cancer
hasn't started to spread into the surrounding tissues. Sometimes stage 2 means
that cancer cells have spread into lymph nodes close to the tumour. This depends
on the particular type of cancer
• Stage 3 usually means the cancer is larger. It may have started to spread into
surrounding tissues and there are cancer cells in the lymph nodes nearby.
• Stage 4 means the cancer has spread from where it started to another body
organ. For example to the liver or lung. This is also called secondary or metastatic
cancer
• Sometimes doctors use the letters A, B or C to further divide the number
categories. For example, stage 3B cervical cancer.
Carcinoma in situ
• Carcinoma in situ is sometimes called stage 0 cancer or 'in situ
neoplasm'.
• It means that there is a group of abnormal cells in an area of
the body.
• The cells may develop into cancer at some time in the future.
• The changes in the cells are called dysplasia.
• The number of abnormal cells is too small to form a tumour.
• The progression begins with a mutation that makes the cell more likely to
divide.
• The altered cell and its descendants grow and divide too often, a condition
called hyperplasia.
• At some point, one of these cells experiences another mutation that
further increases its tendency to divide; this cell's descendants divide
excessively and look abnormal, a condition called dysplasia.
• As time passes, one of the cells experiences yet another mutation, causing very
abnormal structure, loss of differentiation, and loss of contact between the cells;
however, it is still confined to the epithelial layer from which it arose, so it is
called a cancer in situ.
• The in situ cancer may remain contained indefinitely, but additional mutations
may occur that enable it to invade neighboring tissues and shed cells into the
blood or lymph, the tumor is said to be an invasive cancer (malignant).
• The escaped cells may establish new tumors (metastases) at other locations in
the body.
• Normal cells may become cancer
cells. Before cancer cells form in
tissues of the body, the cells go
through abnormal changes called
hyperplasia and dysplasia.
• In hyperplasia, there is an increase in
the number of cells in an organ or
tissue that appear normal under a
microscope.
• In dysplasia, the cells look abnormal
under a microscope but are not
cancer.
• Hyperplasia and dysplasia may or may
not become cancer.
Dysplasia on a Biopsy from the Uterine Cervix
Dysplasia on a Pap Smear