“…Daniels et al (1972) realised that the more necrotic the tissue the less aggressive the tumour, since arteries supplying the tumour were more sclerosed, narrower and thus prevented the formation of metastases. Several authors (Boczko et al, 1979;Krieger et al, 1979;Tsung and Lin, 1983) have tried to establish a connection between hypovascularity , necrosis, calcification and chronicity with the less aggressive pattern of PRA. Folkman (1976) suggested that it lacked the tumour angiogenesis factor (TAF), which prevented potential metastasis.…”