Overexpression of CD38 has been well documented not only in several hematological malignancies, including multiple myeloma (MM), lymphomas, and leukemias, but also in some solid tumors, such as prostate cancer and glioblastoma (GBM), while in other cancer types it can be found within the tumor microenvironment (TME). This evidence concerns the gene CD38 and plasma cell myeloma.