Invasive tests are used to obtain bone marrow, cerebrospinal fluid, thoracoabdominal fluid and some tissue cells by using some invasive means (such as bone puncture, lumbar puncture, thoracoabdominal puncture, ultrasound-guided puncture, needle aspiration biopsy, excisional examination, etc.) during the consultation and treatment process to make a definite diagnosis by visual observation, laboratory tests, histological examination, and some are also therapeutic, such as intrathecal injection for meningeal prophylaxis. Many parents refuse these tests because of lack of knowledge in this area and fear of pain, adverse reactions or danger to the child. Unbeknownst to them, this often prevents the child from receiving timely and correct diagnosis and treatment. For many children with malignant tumors, these invasive tests are very necessary. For example, in case of unexplained severe anemia and suspected leukemia or lymphoma, bone marrow aspiration smear can often make clear diagnosis and staging; neuroblastoma often occurs in early bone marrow metastasis and causes anemia, bone marrow aspiration reveals tumor cells in the form of “daisy clusters” changes can be detected and diagnosed early before symptoms of the primary tumor appear; lumbar puncture and intrathecal injection can make effective means of meningeal prophylaxis in children with leukemia and lymphoma. Repeatedly performing these tests during the treatment process helps to judge the treatment effect and disease progression as a reference for developing and modifying the treatment plan. These treatments can be traumatic for the child, but usually do not cause serious complications. Parents should weigh the pros and cons and not refuse invasive tests for unnecessary concerns, which may delay diagnosis and treatment causing lifelong regrets.