Carcinoma

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In medicine, carcinoma is any cancer that arises from epithelial cells, as opposed to a sarcoma which arises from connective or supportive tissue. It is malignant by definition: carcinomas invade surrounding tissues and organs, and may spread to lymph nodes and distal sites (metastasis). A tumor which appears malignant but does exhibit invasive properties is termed carcinoma in situ (CIS).

Contents

1 Types of carcinoma

1.1 By histology
1.2 By location

2 Histology

3 Staging

4 See also

Types of carcinoma

By histology

Adenocarcinoma is cancer that starts in cells of glandular (secretory) tissue that lines some internal organs; it is the main type of breast cancer and most colorectal cancer.
Squamous cell carcinoma describes the various cancers of squamous cells, thin, flat cells found in many parts of the body. There is squamous cell carcinoma of the lung, the esophagus, the skin, etc.
Adenoid cystic carcinoma

By location

Basal cell carcinoma is cancer of the basal cells of the epidermis. It burrows into the skin, but does not metastasize to other parts of the body.
Cholangiocarcinoma is cancer of the bile duct.
Hepatocellular carcinoma is cancer of the liver. It is often associated with alcohol abuse or hepatitis.
Adrenocortical carcinoma is a cancer of the cortex (outer layer) of the adrenal gland.
Clear cell carcinoma occurs in the vagina
Oat cell carcinoma is also known as "small cell carcinoma". It is a form of bronchogenic carcinoma (cancer of the bronchi of the lung).
Renal cell carcinoma is a form of kidney cancer.

Histology

Carcinomas are recognised on light microscropy by their atypia (cells losing their peculial characteristics), appearance of the nucleus, and various other characteristics. It is deemed malignant when it can be seen invading other structures, e.g. crossing the basal lamina. Very atypical lesions that do not appear to be invasive are termed carcinoma in situ.

Most carcinomas stain positive for cytokeratin. Additionally, specific immunohistochemical markers may reveal the nature of the malignancy, especially when its origin is uncertain. Breast cancer lesions often express the estrogen receptor and the progesterone receptor (although negative staining does note rule it out).

Unknown primary is a malignancy of which the origin cannot be determined. It can occur in any organ, but frequently affects the liver and brain, as well as the lungs.

Staging

Carcinomas, like all cancers, are "staged" according to the extent of disease. This is different for every histological type of cancer, but generally:

T reflects the tumor size (usually 0-3).
N reflects the number of local lymph nodes affected.
M reflects the presence of distal metastasis (0: not, 1: yes).

If any of these determinants are unknown, a question mark is used. Therefore, if metastasis has not been confirmed nor rules out, T1N1M? would be acceptable notation (although the presence of lymph node spread should prompt the search for secondaries).

Staging is an essential step in oncological care, because the stage of the tumor is the main determinant of prognosis and may inform the decision to pursue chemotherapy, radiation therapy or immunotherapy.