The invention pertains to the field of medicine, particularly to methods for suppressing the growth of tumors, which comprise blocking the pathological pathway of human fibroblast growth factor/receptor 1 (domains II and IIIc), and for diagnosing malignant neoplasms leading to an excessive proliferation of tumor cells and to the formation of new vessels accompanied by the growth of primary tumors and metastases. This pathway also represents an independent mechanism of tumor resistance to preparations acting on other pathological pathways. Blocking the aforementioned pathway using various substances that neutralize the receptor by bonding only with domains II and IIIc thereof results in the interruption or slow-down of tumor growth. This receptor can also be used as a target for delivery of diagnostic agents being largely present in tumor cells. The invention enables developing new agents for diagnosing and treating diseases related to excessive proliferation and neovascularization.