Carcinoma is the medical term for the most common type of cancer occurring in humans. Put simply, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that generally arises from cells originating in the endodermal or ectodermal germ layer during embryogenesis. More specifically, a carcinoma is tumor tissue derived from putative epithelial cells whose genome has become altered or damaged to such an extent that the cells become transformed, and begin to exhibit abnormal malignant properties.
- 1. Pathogenesis of Cancer
Cancer occurs when a single progenitor cell accumulates mutations and other changes in the DNA, histones, and other biochemical compounds that make up the cell’s genome. The cell genome controls the structure of the cell’s biochemical components, the biochemical reactions that occur within the cell, and the biological interactions of that cell with other cells. Certain combinations of mutations in the given progenitor cell ultimately result in that cell (also called a cancer stem cell) displaying a number of abnormal, malignant cellular properties that, when taken together, are considered characteristic of cancer, including:
- the ability to continue to divide perpetually, producing an exponentially (or near- exponentially) increasing number of new malignant cancerous “daughter cells” (uncontrolled mitosis);
- the ability to penetrate normal body surfaces and barriers, and to bore into or through nearby body structures and tissues (local invasiveness);
- the ability to spread to other sites within the body (metastasize) by penetrating or entering into the lymphatic vessels (regional metastasis) and/or the blood vessels (distant metastasis).
If this process of continuous growth, local invasion, and regional and distant metastasis is not halted via a combination of stimulation of immunological defenses and medical treatment interventions, the end result is that the host suffers a continuously increasing burden of tumor cells throughout the body. Eventually, the tumor burden increasingly interferes with normal biochemical functions carried out by the host’s organs, and death ultimately ensues.
Malignant neoplasms are exceptionally heterogeneous entities, reflecting the wide variety, intensity, and potency of various carcinogenic promoters. To date, no simple and comprehensive method for classifying them has yet been devised and accepted within the scientific community. Traditionally, however, malignancies have generally been classified into various taxa using a combination of criteria, including:
One commonly used classification scheme classifies these major cancer types on the basis of cell genesis, specifically:
- Their (putative) cell (or cells) of origin
- Epithelial cells => carcinoma
2. Non-hematopoietic mesenchymal cells => sarcoma
- Hematopoietic cells
- bone marrow-derived cells that normally mature in the bloodstream => Leukemia
- bone marrow-derived cells that normally mature in the lymphatic system =>
- Germ cells => Germinoma
Other criteria that play a role in a cancer diagnosis include:
- The degree to which the malignant cells resemble their normal, untransformed counterparts
- the appearance of the local tissue and stromal architecture
- the anatomical location from which tumors arise
- genetic, epigenetic, and molecular features
Histological Types and Variants of Carcinoma
Adenocarcinoma: (adeno = gland) Refers to a carcinoma featuring microscopic glandular- related tissue cytology, tissue architecture, and/or gland-related molecular products, e.g., mucin.
Squamous cell carcinoma: Refers to a carcinoma with observable features and characteristics indicative of squamous differentiation (intercellular bridges, keratinization, squamous pearls).
Adenosquamous carcinoma: Refers to a mixed tumor containing both adenocarcinoma and squamous cell carcinoma, wherein each of these cell types comprise at least 10% of the tumor volume.
Anaplastic carcinoma: Refers to a heterogeneous group of high-grade carcinomas that feature cells lacking distinct histological or cytological evidence of any of the more specifically differentiated neoplasms. These tumors are referred to as Anaplastic or Undifferentiated carcinomas.
Large cell carcinoma: Composed of large, monotonous rounded or overtly polygonal- shaped cells with abundant cytoplasm.
Small cell carcinoma: Cells are usually round and are less than approximately 3 times the diameter of a resting lymphocyte and little evident cytoplasm. Occasionally, small cell malignancies may themselves have significant components of slightly polygonal and/or spindle- shaped cells.
There are a large number of rare subtypes of anaplastic, undifferentiated carcinoma. Some of the more well known include the lesions containing pseudo-sarcomatous components: spindle cell carcinoma (containing elongated cells resembling connective tissue cancers), giant cell carcinoma (containing huge, bizarre, multinucleated cells), and sarcomatoid carcinoma (mixtures of spindle and giant cell carcinoma). Pleomorphic carcinoma contains spindle cell and/or giant cell components, plus at least a 10% component of cells characteristic of more highly differentiated types (i.e. adenocarcinoma and/or squamous cell carcinoma). Very rarely, tumors may contain individuals components resembling both carcinoma and true sarcoma, including carcinosarcoma and pulmonary blastoma.
- 3. Frequent Organ Sites of Carcinoma
- Lung: Carcinoma comprises > 98% of all lung
- Breast: Nearly all breast cancers are ductal
- Prostate: The most common form of carcinoma of the prostate is
- Colon and rectum: Nearly all malignancies of the colon and rectum are either adenocarcinoma or squamous cell
- Pancreas: Pancreatic carcinoma is almost always of the adenocarcinoma type and is highly
Some carcinomas are named for their or the putative cell of origin, (e.g. hepatocellular carcinoma, renal cell carcinoma).
- 4. Types of Carcinoma
1. Epithelial neoplasms
- Squamous cell neoplasms
- Squamous cell carcinoma: Squamous cell carcinoma (SCC or SqCC) is a cancer of a kind of epithelial cell, the squamous These cells are the main part of the epidermis of the skin, and this cancer is one of the major forms of skin cancer. However, squamous cells also occur in the lining of the digestive tract, lungs, and other areas of the body, and SCC occurs as a form of cancer in diverse tissues, including the lips, mouth, esophagus, urinary bladder, prostate, lung, vagina, and cervix, among others. Despite sharing the name squamous cell carcinoma, the SCCs of different body sites can show tremendous differences in their presenting symptoms, natural history, prognosis, and response to treatment.
- Basal cell carcinoma: Basal-cell carcinoma (BCC), a skin cancer, is the most common It rarely metastasizes or kills. However, because it can cause significant destruction and disfigurement by invading surrounding tissues, it is still considered malignant.
- Adenocarcinoma: Adenocarcinoma is a cancer of an epithelium that originates in glandular Epithelial tissue includes, but is not limited to, the surface layer of skin, glands and a variety of other tissue that lines the cavities and organs of the body. Epithelium can be derived embryologically from ectoderm, endoderm or mesoderm. To be classified as Adenocarcinoma, the cells do not necessarily need to be part of a gland, as long as they have secretory properties. Well differentiated adenocarcinomas tend to resemble the glandular tissue that they are derived from, while poorly differentiated adenocarcinomas may not.
- Linitis plastica: Linitis plastica, also known as Brinton’s disease or leather bottle stomach, is a morphological variant of diffuse (or infiltrating) stomach Causes of linitis plastica could be lye ingestion or metastatic infiltration of the stomach, particularly breast and lung carcinoma.
- Vipoma: A VIPoma (also known as Verner Morrison syndrome, after the physicians who first described it) is a rare (1 per 10,000,000 per year) endocrine tumor, usually (about 90%) originating from non-β islet cell of the pancreas, that produce vasoactive intestinal peptide (VIP). It may be associated with multiple endocrine neoplasia type
- Cholangiocarcinoma: Cholangiocarcinoma is a medical term denoting a form of cancer that is composed of mutated epithelial cells (or cells showing characteristics of epithelial differentiation) that originate in the bile ducts which drain bile from the liver into the small Other biliary tract cancers include pancreatic cancer, gallbladder cancer, and cancer of the ampulla of Vater. Cholangiocarcinoma is a relatively rare neoplasm that is classified as an adenocarcinoma (a cancer that forms glands or secretes significant amounts of mucins). It has an annual incidence rate of 1–2 cases per 100,000 in the Western world, but rates of cholangiocarcinoma have been rising worldwide over the past several decades.
- Hepatocellular carcinoma: Hepatocellular carcinoma (HCC, also called malignant hepatoma) is the most common type of liver Most cases of HCC are secondary to either a viral hepatitis infection (hepatitis B or C) or cirrhosis (alcoholism being the most common cause of hepatic cirrhosis).
- Adenoid cystic carcinoma: Adenoid cystic carcinoma (AdCC) is a rare type of cancer that can exist in many different body It most often occurs in the areas of the head and neck, in particular the salivary glands; but has also been reported in the breast, lacrimal gland of the eye, lung, brain, bartholin gland, trachea, and the paranasal sinuses. It is sometimes referred to as adenocyst, malignant cylindroma, adenocystic, adenoidcystic, ACC, AdCC.
- Renal cell carcinoma: Renal cell carcinoma (RCC, also known as hypernephroma) is a kidney cancer that originates in the lining of the proximal convoluted tubule, the very small tubes in the kidney that transport GF (glomerular filtrate) from the glomerulus to the descending limb of the RCC is the most common type of kidney cancer in adults, responsible for approximately 80% of cases. It is also known to be the most lethal of all the genitourinary tumors. Initial treatment is most commonly a radical or partial nephrectomy and remains the mainstay of curative treatment. Where the tumor is confined to the renal parenchyma, the 5-year survival rate is 60-70%, but this is lowered considerably where metastases have
spread. It is relatively resistant to radiation therapy and chemotherapy, although some cases respond to immunotherapy. Targeted cancer therapies such as sunitinib, temsirolimus, bevacizumab, interferon-alpha, and sorafenib have improved the outlook for RCC (progression-free survival), although they have not yet demonstrated improved survival.
(h) Grawitz tumor
- Adnexal and Skin appendage Neoplasms
- Mucoepidermoid Neoplasms
- Cystic, Mucinous and Serous Neoplasms
- Ductal, Lobular and Medullary Neoplasms
- Acinar cell neoplasms
- Complex epithelial neoplasms
- Cancer-Treatment of Choice