Do you think i should ask my pediatrician to test my daughters blood for cancer?

Confusing question: A kid's evaluation for cancer would involve a thorough history, physical and a selection of tests based on hx and px. A "blood"test might be part of the process but a simple CBC will not yield much data unless the kid has leukemia.You should share your concerns with the doc and decide on a proper set of studies to answer your questions.

In short...: There is no such test. Cancer is a collection of diagnoses, each with its own diagnostic criteria, and few with a specific, singular diagnostic test. Moreover, screening tests rarely have much utility unless the suspected disease is enriched in the population being tested. If there is a clinical concern or suspicion you should raise it with your physician. Know that cancer is uncommon in kids.

Why?: Why do you ask? There are no specific blood tests for cancer. Blood counts can be done to evaluate for leukemia and other tumors that have replaced normal bone marrow. Children with bone marrow replacement due to leukemia or metastatic tumor are clinically sick (fever, pain, bruising/bleeding). Clinically well children rarely have blood tests that are diagnostic of cancer.