Carcinomes

Carcinomes (carcinomas) are malignant tumors that arise from epithelial cells, the tissues that line the surfaces and cavities of organs and form glands. They are the most common category of cancer worldwide, accounting for the majority of solid tumors in adults. Carcinomas can develop in many sites, including the skin, lungs, breast, colon, pancreas, and urinary or reproductive tract.

Most carcinomas originate from either squamous epithelium or glandular epithelium. The main histologic subtypes include squamous cell carcinoma (from squamous cells, common in skin, lungs, and mucosal surfaces), adenocarcinoma (gland-forming, common in breast, lung, colon, and pancreas), basal cell carcinoma (from basal cells of the skin), and transitional cell carcinoma (from urothelial lining, in the urinary tract). Other organs have their own characteristic carcinomas, such as hepatocellular carcinoma in the liver and renal cell carcinoma in the kidney.

Pathogenesis typically involves genetic and epigenetic alterations that drive uncontrolled cell growth. Common events include mutations in tumor suppressor genes and oncogenes, chromosomal instability, and dysregulated signaling pathways. The disease often progresses from normal epithelium to dysplasia, carcinoma in situ, and invasive carcinoma, with potential spread to regional lymph nodes or distant organs (metastasis).

Staging follows the TNM system, describing tumor size/extent (T), nodal involvement (N), and metastasis (M). Treatment is site- and stage-dependent, and may include surgery, radiotherapy, chemotherapy, targeted therapies, or immunotherapy. Early-stage carcinomas amenable to complete resection have the best prognosis; advanced disease has a more variable and generally poorer outcome.

Prevention and risk reduction focus on eliminating or mitigating well-established risk factors, such as tobacco use, chronic infections, ultraviolet exposure, and obesity.