A pathogenic agent, which spread from one site to another site inside the host body. And the newly pathologic sites are said to be metastases. Cancer is generated if any sort of alteration is there genetically which results in the proliferation uncontrollably by mitosis thus primary heterogeneic tumor is produced. The cells which has tumors it undergoes various metabolic changes metaplasia, then dysplasia then anaplasia, which is a malignant phenotype. This undergoes into blood circulation which is followed by the tumorigenesis to the secondary site. Some of the cancerous cells used to penetrate through the vessels to the different sites like organs or tissues within the body called as hematogenous spread. Thus when the cells of tumors come to the resting state, this penetrate to other site and thus continues its spreading process by multiplying and thus form new tumors too, thus tumor said to be metastatic tumor or secondary tumor.