The most common type of cancer in humans is carcinoma. Carcinoma is a cancer that begins in tissue that lines the inner or outer surfaces of the body.
Generally, carcinoma arises from cells originating in the endodermal or ectodermal germ layer during embryogenesis. Specifically, carcinoma is tumor tissue derived from putative epithelial cells whose genome has become altered or damaged, causing the cells to transform and show abnormal malignant properties.
Malignant tumors made up of transformed cells whose origin or developmental lineage is unknown but have specific molecular, cellular and histological characteristics typical of epithelial cells are also characterized as carcinoma.
Organ sites frequently affected by carcinomas include:
• colon and rectum; and
Carcinoma is diagnosed using biopsy, such as fine-needle aspiration, core biopsy or subtotal removal of a single node. A pathologist then analyzes the sample under a microscope to identify molecular, cellular or tissue architectural characteristics of epithelial cells.
Types of carcinomas
The different types of carcinomas include:
• squamous cell carcinoma (carcinoma with observable features indicative of squamous differentiation);
• adenosquamous carcinoma (a mixed tumor with adenocarcinoma and squamous cell carcinoma);
• anaplastic carcinoma (a heterogeneous group of high-grade carcinomas featuring cells that lack distinct histological or cytological evidence of more specifically differentiated neoplasms);
• large-cell carcinoma (large, monotonous rounded or polygonal-shaped cells with abundant cytoplasm);
• adenocarcinoma (glandular); and
• small-cell carcinoma (round cells three times the diameter of a resting lymphocyte and little evident cytoplasm).
Carcinoma in situ
Carcinoma in situ is the term for a small, localized carcinoma that has not invaded through the epithelial basement membrane restricting the carcinomatous cells from adjacent normal cells. This type of carcinoma is pre-invasive but not pre-malignant. Carcinoma in situ almost always continues to grow and progress until it infiltrates and penetrates into and through the basal membrane or other structures. Once the basal membrane or other structures are penetrated, these lesions are no longer considered carcinoma in situ, but invasive carcinomas. Cure rates for carcinoma in situ may be 100% if lesions can be removed using surgical resection, cryotherapy, laser ablation or other local treatment before metastasis.
Adenocarcinoma initiates in the secretory or glandular cells of the body. Glandular cells are a part of the tissue that lines certain internal organs. These cells create and release substances within the body, like digestive juices or mucus. Adenocarcinomas are most often found in the breast, colon, lung, pancreas and prostate.
Carcinomatosis occurs when a cancer has spread throughout the body or when a cancer has spread to a significant region of the body. A specific type of carcinomatosis is peritoneal carcinomatosis. This type of carcinomatosis occurs when a cancer metastasizes and manifests in carcinomas of the gastrointestinal tract and ovaries.
Treatment of carcinoma will differ depending on type and location.
Possible treatments include:
• targeted cancer therapy; and
• biologic therapy.
Support groups are also available to help patients cope with the anxiety that often accompanies a cancer diagnosis.
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