Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)

by Jason Wasserman MD PhD FRCPC
January 25, 2023

What is non-invasive follicular thyroid neoplasm with papillary-like nuclear features?

Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is a non-invasive type of thyroid cancer. It is called ‘non-invasive’ because when examined under the microscope, there is a clear separation between the tumour and the surrounding normal thyroid gland tissue.

Is non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) a type of cancer?

NIFTP is a non-invasive type of thyroid cancer. However, unlike other types of thyroid cancer, it has a very low malignant potential which means it is very unlikely to spread to lymph nodes or other parts of the body. In addition, most patients with NIFTP are cured by surgery alone.

What is the difference between non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) and non-invasive encapsulated follicular variant papillary thyroid carcinoma (EEVPTC)?

Until 2016, NIFTP was called non-invasive encapsulated follicular variant papillary thyroid carcinoma (EFVPTC). At that time, it was also considered a type of thyroid cancer. The tumour was described as non-invasive because the entire tumour was surrounded by a capsule and the tumour cells were not seen spreading into or invading the normal thyroid tissue. The name and classification were changed after several large, scientific studies found that patients diagnosed with non-invasive EFVPTC could be cured with surgery alone.

How do pathologists make the diagnosis of non-invasive follicular thyroid neoplasm with papillary-like nuclear features?

The diagnosis of NIFPT can only be made after the entire tumour is removed and sent for examination under the microscope by a pathologist. This examination needs to be performed in order to make sure that the tumour cells do not cross the tumour capsule or spread into the normal surrounding thyroid tissue. The diagnosis cannot be made after a small tissue sample is removed from the thyroid gland in a procedure called fine-needle aspiration.

What does non-invasive follicular thyroid neoplasm with papillary-like nuclear features look like when examined under the microscope?

When examined under the microscope, the tumour cells in NIFTP are often separated from the surrounding normal thyroid gland by a thin tissue barrier called a tumour capsule. If no capsule is seen, the tumour cells should still be separated from the normal thyroid gland by a small space.

Like the normal thyroid gland, NIFTP is made up of follicular cells that connect together to form follicles. The follicular cells show changes that pathologists describe as “papillary-like nuclear features” because they look similar to the cells in a type of cancer called papillary thyroid carcinoma.

In these cells, the part of the cell that holds the genetic material, the nucleus, is larger and the genetic material or chromatin is pushed to the edge of the nucleus. Pathologists describe this change as chromatin clearing. The outer border or membrane of the nucleus is often irregular in shape and lines or grooves can be seen running down the middle of the cells. Finally, unlike normal, healthy follicular cells, the cells are crowded which causes the nuclei to overlap.

Exclusion criteria

Your pathologist also needs to examine the tumour to ensure it does not have other features that are seen in cancers of the thyroid gland but not in NIFTP. Pathologists call these features exclusion criteria and they include:

• Papilla – A papillae (papillae means one, multiple are called papilla) is a group of cells connected together to form a piece of tissue that looks like a finger sticking out into the air. The centre of the finger is usually made up of small blood vessels and connective tissue. Papilla are very commonly seen in a type of cancer called papillary thyroid carcinoma and are not seen in NIFTP.
• Psammoma bodies – A psammoma body is a small round structure made up of dead cells and calcium. It looks dark purple when examined under the microscope. Psammoma bodies are very commonly seen in a type of cancer called papillary thyroid carcinoma and are not seen in NIFTP.
• Vascular invasion – Vascular invasion means that some of the tumour cells have entered a blood vessel. Once inside a blood vessel, the tumour cells are able to spread to other parts of the body. Because vascular invasion is a way for tumour cells to spread outside of the tumour, it should not be seen in NIFTP.
• Lymphatic invasion – Lymphatic invasion means that some of the tumour cells have entered a small channel called a lymphatic vessel. Lymphatics are connected to small organs called lymph nodes. Once inside a lymphatic channel, the tumour cells are able to spread to nearby lymph nodes. Because lymphatic invasion is a way for tumour cells to spread outside of the tumour, it should not be seen in NIFTP.

Can the cells from this tumour spread to other parts of the body?

Once removed completely, the cells in an NIFTP should not be able to spread to other parts of the body. Patients with NIFTP alone also do not require additional surgery or treatment with radioactive iodine.

However, for a small number of patients initially diagnosed with NIFTP, tumour cells will be found later in a lymph node or other part of the body. Tumour cells that spread to a lymph node or other part of the body are called metastasis. When this happens, it is likely that a small area of tumour capsule invasion was not seen when the tumour was examined. In this situation, the original diagnosis may need to be changed.