What is Carcinoma?

The most common type of cancer that develops from epithelial cells

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Carcinoma is one of five major types of cancer that develop in cells that line the outer surface of organs, which are known as epithelial cells. It accounts for 80% to 90% of all cancer diagnoses. Epithelial cells line the outer surface of the skin, as well as canals and hollow structures, such as blood vessels, organs, and the abdominal cavity. The other four cancer types are sarcoma, leukemia or lymphoma, blastomas, and germ cell tumors. Each of them affects a different type of cells.

Carcinoma cells multiply rapidly and form a solid mass (a tumor). The progression of the disease is described in stages, while the characteristics of the cells, described in grades, predict how aggressive or indolent (slow-growing) the malignancy will be.

A doctor and cancer patient review test results.
 Fatcamera / Getty Images

Types

There are three major types of carcinoma, including adenocarcinoma, basal cell carcinoma, and squamous cell carcinoma. 

Adenocarcinoma

Adenocarcinoma is a type of cancer affecting glandular tissues, and can cause breast, lung, colorectal, stomach, prostate, pancreatic, and esophageal cancer, among others. Hepatocellular carcinoma (liver cancer), renal cell carcinoma (kidney cancer), cholangiocarcinoma (bile duct cancer) are common types of adenocarcinoma.

Basal cell carcinoma (BCC)

Basal cell carcinoma is the most common type of skin cancer. It affects basal cells (which produce new skin cells) in the lower part of the epidermis (surface level of the skin). For most people, BCC is not life-threatening. It tends to grow slowly, and it seldom spreads to another part of the body. When found early, this skin cancer is highly treatable.

Squamous cell carcinoma (SCC)

Also known as epidermoid carcinoma, squamous cell carcinoma affects squamous cells (which make up the epidermis) and can cause skin, lung, oral head and neck, esophageal, cervical, vaginal, bladder, prostate, and penile cancer. It is the second most common form of skin cancer after BCC.

Carcinoma types vary not only by the organs they affect but also by their rate of progression. BCC tends to be slow-growing and least likely to spread, while SCC is generally faster-growing than adenocarcinoma. But many molecular, cellular, hormonal, and physiologic factors can alter the rate by which these and other cancers progress and spread.

There are also variations in carcinoma cell types—such as adenosquamous carcinomas, anaplastic carcinoma, small cell carcinoma, and large cell carcinoma—the features of which can predict the aggressiveness of the disease. 

Common Types of Carcinoma

The majority of breast, colorectal, kidney, liver, lung, oral, pancreatic, and prostate cancers are carcinoma.

Cause

Multiple genetic mutations can accumulate in a progenitor cell (a cell, like a stem cell, that can differentiate to create a specialized cell), and certain combinations of mutations can lead to the development of a cancer stem cell, which produces cancer cells and causes cancer.

These cancer cells have distinctive properties:

  • They are effectively “immortal” and do not die of programmed cell death (apoptosis) like normal cells do
  • They can reproduce exponentially because their growth is unchecked
  • They have the ability to penetrate surfaces and directly invade nearby structures
  • They have the ability to metastasize (spread) from the site of the original tumor to distant sites, typically when cancer cells break off and are distributed through the bloodstream or lymphatic system

When the mutations occur in the progenitor cells of the epithelium, they may produce a benign tumor (such as an adenoma) or a malignant one (carcinoma).

The reason why these mutations occur is not entirely clear. They are believed to be the result of a combination of factors, including:

In certain cancers, age plays a central role. This is especially true with carcinomas, the risk of which increases with age. According to the National Cancer Institute, the median age of diagnosis for breast cancer is 61 years old, 68 years old for colorectal cancer, 70 years old for lung cancer, and 66 years old for prostate cancer. All of these are predominantly associated with carcinoma.

Is Carcinoma Common in Children?

Unlike some forms of cancer, such as leukemia, carcinomas are exceptionally rare in children, accounting for less than 1% of cases.

Scientists have yet to determine which combination of mutations leads to cancer, but have begun to identify specific mutations linked to various cancers. A genetic mutation linked to carcinoma is BRCA mutations.

Diagnosis

Although a variety of tests can be used to screen for carcinomas in different parts of the body—including imaging studies (mammograms, CT, MRI), lab tests (cytology, PSA), and procedures (colonoscopy, thoracentesis)—carcinomas are definitively diagnosed based on an examination of the cancer cells under the microscope. 

Carcinomas involve solid tumors, so the investigation typically includes a biopsy (when cells or tissue are taken from your body to be examined under a microscope), which is performed to extract a tissue sample and morphology (physical structure) to identify the molecular, cellular, and architecture characteristics of the affected cells and tissues. 

Going through a biopsy does not mean that you have cancer. The process of closer examination using a microscope is called histology.

Types of biopsies include:

  • Bone Marrow Biopsy: Using a biopsy needle, your doctor will withdraw a sample of bone marrow tissue. This procedure is usually done under local anesthesia
  • Endoscopic Biopsy: An endoscope is a flexible tube with a light attached, and can help to reach locations such as the lung or bladder
  • Needle Biopsy: When a doctor is able to feel a tumor through your skin, a needle biopsy may be used. Types of needle biopsies include fine-needle, core needle, vacuum-assisted, and image-guided
  • Skin Biopsy: Most often used to diagnose skin conditions, a skin biopsy removes cells from your body’s surface
  • Surgical Biopsy: If other biopsy methods are not an option, or if they have produced inconclusive results, a surgical biopsy is often used. During this type of biopsy, an incision is made to remove a portion of the cells in question for further examination

Carcinomas can be differentiated based on their morphology through tests, including:

  • Gross Examination: An evaluation of the biopsy specimen with the naked eye
  • Frozen Section: A pathologist freezes and examines the tissue. It is often used for rapid diagnosis during surgery
  • Histologic Description: A microscopic view is used to classify the abnormality of the tissue
  • Cytology Description: Cytology looks at cells, and can detect small changes at the cellular level to identify cancerous or precancerous cells. It can be used to detect the presence of abnormal cells, which may or may not be cancerous but can increase cancer risk

The differentiation of carcinoma cells can predict how aggressive or indolent cancer may be. Well-differentiated means the cells behave and act like normal cells, and the cancer is likely to develop slowly. Undifferentiated means the cells are very immature and primitive, and they lack the features used to identify and classify different cancers. An undifferentiated cancer is more malignant than a cancer that is well differentiated.

These tests are used to not only diagnose carcinomas but also stage and grade the disease.

Cancer Staging and Grading

Staging and grading describe both the severity and likely course of the disease, which in turn directs the appropriate course of treatment.

Staging

Cancer staging is a method of categorizing the extent of cancer’s spread in the body. The majority of solid tumors are staged as follows:

  • Stage 0: The cancer is only located in the original tumor and has not spread
  • Stage I: The cancer has not spread to neighboring tissues nor the lymph nodes
  • Stages II & III: The cancer has spread to neighboring tissues and potentially the lymph nodes
  • Stage IV: The cancer may have spread to other organs and may also be referred to as metastasized cancer

Small cell lung carcinoma (SCLC) only has two stages: limited and extensive.

Grading

Cellular characteristics inform the cancer stage and prognosis by assigning a tumor grade. The tumor grade helps determine the best treatment.

The grades include:

  • Grade 1: The cancer cells look similar to normal cells (well-differentiated) and are growing slowly
  • Grade 2: The cancer cells present with a higher degree of abnormality and the growth is more rapid
  • Grade 3: The cells are now poorly differentiated
  • Grade 4: The cells are undifferentiated and may be growing quickly

Treatment

The treatment of carcinoma depend on the location and size of the tumor, the stage and grade of the disease, and the performance status of the individual.

The general treatment approaches include:

  • Chemotherapy: Chemotherapy is a drug treatment to eliminate the fast-growing cancer cells. Neoadjuvant refers to chemotherapy that is given prior to surgery. Adjuvant refers to chemotherapy that is administered post-surgery
  • Radiation Therapy: Adjuvant refers to radiation therapy given post-surgery. Palliative radiation can be given to ease suffering to improve quality of life
  • Surgery: Surgical resection typically provides the best chance of long-term survival in the early stages
  • Immunotherapy: There are two main types of immunotherapy: active and passive. Active immunotherapy activates your body’s immune system to fight cancer cells. Examples of active immunotherapy include cancer vaccines and adoptive cell therapy. Passive immunotherapy uses components made in a lab to help your body respond to cancer in the way it should. Examples of passive immunotherapy include cytokines (proteins involved in cell signaling) and immune checkpoint inhibitors.
  • Hormonal Therapy: Both breast and prostate cancer cells use hormones to grow. Hormone therapy can be used to decrease the size of a tumor prior to surgery (neoadjuvant therapy), improve chances of remission, and kill cancer cells that have returned. There are two main kinds of hormonal therapies: One blocks hormone production and the other modifies hormone behavior.

Treatments can have different goals. For example, curative treatments are intended to promote recovery and potentially lead to remission, whilst palliative is intended to reduce suffering. Remission indicates a decrease or disappearance of disease signs and symptoms, while recurrence indicates the return of cancer.

A prognosis is the likely outcome of a disease and may vary by the type and stage of cancer along with other factors. The prognosis is reflected in survival rates, typically five-year survival rates and arguably, more importantly, disease-free survival.

A Word From Verywell

The best tool for cancer prevention is education. By identifying your personal risk factors, including family history, following regular screening guidance such as mammograms, colonoscopy, and low-dose lung CT, and taking the time to learn about the signs and symptoms of cancer, you are more likely to catch cancer early when it is most treatable.

Cancer is still not a curable disease, but there are many options available for people with cancer to manage their disease and continue to live life to the fullest. Enlist the support of family and friends to cope with the stress of not only the diagnosis but also living with cancer, and learn from others who also have cancer about ways to improve quality of life.

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