A tumor is an abnormal growth of body tissue. Tumors can be cancerous or noncancerous. The development of the new biological drugs in the treatment of cancer has recently renewed the concept of “tumor heterogeneityâ€Â. The effects of the new targeted therapy, such as angiogenesis inhibitors and antivascular therapies, are more complex, compared to the well-known cytotoxic drugs. The intra- and inter-tumor heterogeneity, heterogeneity between metastatic disease, and also heterogeneity that happens over time, profoundly influence the treatment outcome of patients. At present, tailored medicine heavily relies on the pathological characterization of tumor by biopsies but we should have multiple biopsies of the same tumor in the same patients, to study the dedifferentiation of a metastatic disease under treatment. Citations are important for a journal to get impact factor. Impact factor is a measure reflecting the average number of citations to recent articles published in the journal. The impact of the journal is influenced by impact factor, the journals with high impact factor are considered more important than those with lower ones. This information can be published in our peer reviewed journal with impact factors and are calculated using citations not only from research articles but also review articles (which tend to receive more citations), editorials, letters, meeting abstracts, short communications, and case reports.