Other meanings of Carcinoma
ONCOLOGY
Carcinoma is cancer that arises from epithelial cells, the cells forming the skin and the linings or coverings of organs, glands, and body passages. It is the most common broad class of malignant tumors and includes diseases with very different causes, appearances, treatments, and outcomes.
Carcinoma is a malignant neoplasm derived from epithelial cells.1 Epithelium covers the body surface, lines structures such as the intestine and airways, and forms secretory glands. The term therefore describes a broad biological category rather than one single disease. Major families include adenocarcinoma, which shows gland formation or related secretory features, and squamous cell carcinoma, which resembles the flat cells of surface epithelium. Other named forms include basal cell carcinoma, urothelial carcinoma, renal cell carcinoma, and hepatocellular carcinoma.
Classification combines the organ of origin, microscopic architecture, cell differentiation, molecular alterations, and clinical behavior. Modern tumor classifications increasingly integrate pathology with molecular findings, because tumors that look similar under a microscope can respond differently to treatment.2
Carcinoma develops when epithelial cells acquire genetic and epigenetic changes that disrupt growth control, DNA repair, cell death, and tissue organization. Persistent exposures such as tobacco smoke, ultraviolet radiation, some infections, and chronic inflammation can contribute, although the causes differ among organs and individual cases.3 A precancerous lesion may precede invasion, but not every abnormal epithelial change progresses to cancer.
Diagnosis usually begins with imaging, endoscopy, cytology, or direct examination and is confirmed by a biopsy. A pathologist evaluates architecture, differentiation, grade, margins, and sometimes lymphovascular or perineural invasion. Immunohistochemistry can identify lineage or therapeutic markers, while genomic testing may reveal alterations relevant to targeted therapy or inherited cancer risk. Staging assesses the primary tumor, regional lymph nodes, and distant metastasis.4
Treatment is selected according to the carcinoma's site, stage, histologic subtype, biomarkers, and the patient's health and preferences. Localized disease is often treated with surgery, radiation therapy, or both; systemic options include chemotherapy, endocrine therapy, immunotherapy, and targeted therapy.5 Some tumors require multimodal treatment because microscopic disease may remain beyond the visible mass.
Prognosis is not determined by the word carcinoma alone. Early detection, complete removal, favorable differentiation, absence of nodal or distant spread, and actionable molecular features can improve prospects, whereas invasion of vital structures or metastatic disease generally makes treatment more complex. Screening is available for selected populations and sites, including colorectal, cervical, breast, and lung cancer, but screening recommendations depend on evidence of benefit and potential harm.
Several less familiar distinctions change the meaning of a carcinoma diagnosis. Carcinoma in situ contains malignant-appearing epithelial cells confined above the tissue boundary known as the basement membrane; it has not yet acquired the defining capacity for stromal invasion, although some forms have substantial risk of progression.1 By contrast, microinvasive carcinoma has crossed that boundary on a very small scale.
Some carcinomas are mixed or unusually differentiated: tumors can contain both glandular and squamous components, while others lose recognizable features and are described as poorly differentiated or undifferentiated. A metastasis may be found before the primary tumor, and its microscopic and molecular profile can help identify the organ of origin. Rare carcinomas also arise in unexpected epithelial sites, including the thymus or specialized skin appendages. These edge cases are why specialist pathology review and organ-specific classification remain important.
Terminology follows contemporary pathology and cancer-classification usage; individual carcinoma subtypes have separate diagnostic criteria and clinical guidelines.
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