Carcinoma

Carcinoma is a malignant tumor that arises from epithelial cells, which line internal organs and body surfaces, or from glandular tissue. Carcinomas account for the majority of cancers worldwide and can develop in many tissues, including skin, lung, breast, colon, and pancreas. They are distinguished from sarcomas, which arise from connective tissues such as bone, muscle, or fat.

Origins and subtypes: Carcinomas arise from epithelial cells that line surfaces and glands. Major subtypes include squamous cell carcinoma (squamous epithelium), adenocarcinoma (glandular epithelium), basal cell carcinoma (skin), urothelial carcinoma (urinary tract lining), hepatocellular carcinoma (liver), pancreatic ductal adenocarcinoma, and renal cell carcinoma (kidney).

Pathology: Carcinomas typically show dysplasia, loss of normal cell polarity, and genetic alterations. They invade through the basement membrane and spread via lymphatic or blood vessels. Molecular drivers vary by tumor type and may involve EGFR, HER2, KRAS, p53, and other pathways.

Risk factors and screening: Risk factors include tobacco use, ultraviolet radiation, human papillomavirus infection, chronic inflammation, obesity, and alcohol. Screening and prevention strategies are organ-specific, such as cervical cytology, mammography, colonoscopy, and vaccination where available.

Diagnosis and staging: Diagnosis relies on biopsy with histopathology; imaging assists staging. The TNM system (tumor size/invasion, nodes, metastasis) is widely used to guide treatment decisions and prognosis.

Treatment and prognosis: Management depends on type and stage. Localized diseases may be cured with surgery and/or radiotherapy; advanced disease often requires systemic therapy, including chemotherapy, targeted therapy, and immunotherapy. Prognosis varies widely, with earlier-stage cancers generally more favorable than metastatic disease.