The treatment of neoplastic diseases is one of the main clinical challenges of modern human and animal medicine. Pathological angiogenesis in tumour tissues and the production of angiogenic factors are recognised as key features responsible for cancer development and metastasis formation. A new network of blood vessels allows cancer cells to efficiently provide nutrients and eliminate metabolic waste products. Thus, the primary tumour can form metastases and spread throughout the body. The main factors stimulating the angiogenesis process are VEGF, FGF, EGF, PDGF, and TGF-β1, with VEGF being the most specific, strongest and most widely studied. The measurement of the expression of pro-angiogenic factors in both humans and animals has diagnostic and prognostic value. Several mechanisms of new blood-vessel formation in cancerous tissue have been identified. The three dominant processes are vascular sprouting, intussusceptive angiogenesis and vessel co-option. Angiogenesis in cancer tissues is still the subject of numerous scientific studies aimed at finding effective anti-angiogenic factors that would inhibit the formation of blood vessels in the tumour as a part of anti-cancer therapy.