WHAT IS NIFTP?
Non-invasive follicular thyroid neoplasm with papillarylike nuclear features (NIFTP) is a new name for a very low risk thyroid tumor previously known as an Encapsulated Non-invasive Follicular Variant Papillary Thyroid Carcinoma. Although the cells in a NIFTP have features that look like papillary thyroid cancer, this finding alone does not mean NIFTPs are malignant. Because NIFTP tumors are not invasive and are contained within the tumor capsule, they are considered to have an extremely low risk of adverse outcomes like tumor recurrence or spread (metastasis). For correct diagnosis, NIFTP tumors must meet very stringent criteria—all related to how the tumor looks under the microscope. Key among these are the following requirements:
- The tumor may not show evidence of invasion. This means the tumor cannot penetrate into its capsule, the blood vessel or the lymphatic channels within the tumor or thyroid.
- The tumor must have a “follicular” growth pattern.
- The entire tumor capsule must be reviewed by the pathologist
- The tumor CAN NOT have any necrosis (i.e. areas of dead tumor cells that can be related to outgrowing its blood supply) or increased mitotic rate (i.e. faster speed of growth).
- The tumor must have no or minimal (<1%) papillary appearance, and CAN NOT have the appearance of other thyroid cancer variants (some examples include insular, oncocytic, tall cell, columnar cell, diffuse sclerosing)