carcinomen

Carcinomas are malignant tumors that arise from epithelial cells, which line internal organs, cavities and glands. They represent the majority of cancers worldwide, reflecting their origin in tissues exposed to environmental factors. Carcinomas can develop in many organs, including the skin, lung, breast, colon, and prostate.

They are classified histologically by the type of epithelial cell involved: adenocarcinoma (gland-forming), squamous cell carcinoma (epithelial squamous lining), basal cell carcinoma (skin), urothelial or transitional cell carcinoma (bladder and urinary tract), and other less common subtypes.

Molecular pathogenesis involves accumulation of genetic and epigenetic alterations that drive uncontrolled growth, resistance to cell death, invasion, and metastasis. Many carcinomas progress from dysplasia to carcinoma in situ before invading surrounding tissue.

Diagnosis relies on tissue biopsy with histopathology, while imaging and laboratory tests aid staging and assessment. Immunohistochemistry and molecular profiling help subtype tumors and guide targeted or immune-based therapies. Staging uses the TNM system to describe tumor size, nodal involvement, and metastasis.

Treatment is site- and stage-dependent. Localized carcinomas may be treated with surgery and/or radiotherapy; advanced disease often requires systemic therapy such as chemotherapy, targeted therapy, or immunotherapy. Choice depends on histology and molecular features (for example EGFR mutations or hormone receptors).

Prevention and risk reduction include avoiding tobacco, protection from ultraviolet radiation, vaccination against oncogenic viruses (HPV, hepatitis B), and participation in cancer screening programs for certain sites. Prognosis varies widely with stage, tumor type, and molecular characteristics.