The term malign (malignant) is used to describe cancerous cells.

The intact blood brain barrier prevents that contrast agents penetrate in the normal brain tissue. If the blood brain barrier is damaged by a malignant tumor, the contrast medium can accumulate within the interstitial tumor tissue due to the alterations in the blood brain barrier permeability. Adjacent normal brain tissue does not contain the contrast agent.

Cancer is a general term related to the abnormal (malignant) growth of cells (tumor) which tend to proliferate uncontrolled and destroy healthy tissues. If not controlled by effective treatment, cancer can spread out into other regions of the body (metastasize).
Ductal carcinoma in situ (DCIS): A form of breast carcinoma in situ confined to the breast ducts. DCIS (also called noninvasive breast cancer or intraductal breast carcinoma) is often associated with microcalcification on mammography.

(FNH) The focal nodular hyperplasia is a hypervascular, benign focal liver lesion. Various liver imaging techniques are common to differentiate FNH from a malign lesion, such as contrast enhanced ultrasound, MRI or a CT multi phase study.

Iodinated contrast media contain small amounts of free iodide. Too much free iodide in the blood may cause hyperthyroidism in patients at risk, but contrast medium induced thyrotoxicosis is rare. The free iodide may also interfere with nuclear medicine diagnostic tests and treatment. However, iodinated contrast agents do not affect thyroid function tests (e.g., T3, T4, TSH) in patients with a normal thyroid.
Guidelines were prepared by the 'Contrast Media Safety Committee of the European Society of Urogenital Radiology' and discussed on the Tenth European Symposium on Urogenital Radiology in September 2003.
Tests of thyroid function before the injection of contrast agents may only be indicated in areas with dietary iodine deficiency. Patients with Graves' disease, multinodular goiter with thyroid autonomy, especially elderly and patients who lives in areas of iodine deficiency are at risk to develop thyrotoxicosis after IV contrast medium and should be monitored by endocrinologists after contrast enhanced CT exams. Prophylaxis may offer some protection in selected high-risk individuals but is not generally recommended.
The free iodide of iodinated contrast agents interferes with thyroidal iodide uptake and impedes diagnostic thyroid scintigraphy and radio-iodine treatment of thyroid malignancies for 2 months after administration.