The study demonstrates that preventing neovascularization can arrest the growth of solid tumors in vivo. Tumors implanted directly on the iris of rabbits vascularized and grew exponentially, while those placed in the anterior chamber remained dormant, growing only to a small size and remaining avascular for up to 6 weeks. This suggests that neovascularization is necessary for malignant growth. The growth of vascular tumors followed a sigmoidal curve with three phases: prevascular, vascular, and late growth. During the prevascular phase, tumors grew slowly due to diffusion, while vascularization allowed exponential growth. Avascular tumors, though containing viable cells, did not grow further due to lack of vascularization. When reimplanted on the iris, these tumors vascularized and grew rapidly. The study indicates that blocking tumor-induced angiogenesis could be an effective strategy for controlling neoplastic growth. The findings highlight the importance of neovascularization in tumor progression and suggest that preventing it may lead to tumor dormancy. The results also imply that clinical instances of delayed metastasis or local recurrence may be related to spontaneous failure of tumor neovascularization. The study provides in vivo evidence that neovascularization is a necessary condition for malignant growth, and that preventing it can lead to tumor dormancy. The results suggest that specific blockade of tumor-induced angiogenesis may be an effective means of controlling neoplastic growth.The study demonstrates that preventing neovascularization can arrest the growth of solid tumors in vivo. Tumors implanted directly on the iris of rabbits vascularized and grew exponentially, while those placed in the anterior chamber remained dormant, growing only to a small size and remaining avascular for up to 6 weeks. This suggests that neovascularization is necessary for malignant growth. The growth of vascular tumors followed a sigmoidal curve with three phases: prevascular, vascular, and late growth. During the prevascular phase, tumors grew slowly due to diffusion, while vascularization allowed exponential growth. Avascular tumors, though containing viable cells, did not grow further due to lack of vascularization. When reimplanted on the iris, these tumors vascularized and grew rapidly. The study indicates that blocking tumor-induced angiogenesis could be an effective strategy for controlling neoplastic growth. The findings highlight the importance of neovascularization in tumor progression and suggest that preventing it may lead to tumor dormancy. The results also imply that clinical instances of delayed metastasis or local recurrence may be related to spontaneous failure of tumor neovascularization. The study provides in vivo evidence that neovascularization is a necessary condition for malignant growth, and that preventing it can lead to tumor dormancy. The results suggest that specific blockade of tumor-induced angiogenesis may be an effective means of controlling neoplastic growth.