Tumors

A tumor is a mass formed by abnormal cell growth. In medicine, tumors are neoplasms, but not all enlargements are tumors. Tumors can be benign, growing slowly and remaining local, or malignant, capable of invading nearby tissues and spreading (metastasizing) to distant sites.

Tumors are classified by tissue of origin. Carcinomas arise from epithelial cells; sarcomas from connective tissue; hematologic malignancies include lymphomas and leukemias; and central nervous system tumors include gliomas. Benign examples include lipomas, fibromas, and adenomas. Some lesions are non-neoplastic, reflecting inflammation, infection, or vascular malformations.

Causes involve genetic mutations, inherited predispositions, and environmental factors such as tobacco use, radiation exposure, carcinogenic chemicals, and infections. Age increases risk. Diagnosis combines imaging (such as ultrasound, CT, or MRI) and histologic examination of tissue obtained by biopsy or surgery, with molecular tests increasingly used to guide classification and treatment. Staging for malignant tumors assesses size, lymph node involvement, and spread to distant organs.

Treatment depends on tumor type and stage. Options include surgery to remove the mass, radiation therapy, and systemic therapies such as chemotherapy, targeted therapy, immunotherapy, and, in some cases, hormone therapy. Some tumors are monitored with active surveillance when growth is slow or uncertain. Prognosis varies widely by tumor type, stage at diagnosis, and molecular characteristics, ranging from highly curable in early disease to more challenging in advanced cases.