Suspicious for follicular neoplasm

by Adnan Karavelic MD FRCPC
November 22, 2022

What does “suspicious for follicular neoplasm” mean?

Suspicious for follicular neoplasm is a term pathologists use to describe an abnormal growth in the thyroid gland. It is a preliminary diagnosis that includes both non-cancerous and cancerous conditions.

These conditions include:

• Adenomatoid nodule – Adenomatoid nodule is a non-cancerous type of growth in the thyroid gland. Most adenomatoid nodules develop as part of a condition called nodular thyroid hyperplasia.
• Follicular adenoma – Follicular adenoma is a non-cancerous type of thyroid tumour. The tumour cells are separated from the normal thyroid gland by a thin tissue barrier called a capsule.
• Follicular carcinoma – Follicular carcinoma is a type of thyroid cancer. Most tumours are at least partially separated from the normal thyroid gland by a thin barrier called a capsule. The tumour cells in follicular carcinoma look similar to the cells in a follicular adenoma. The most important difference is that in follicular carcinoma, the tumour cells cross the capsule and spread into the surrounding thyroid gland.
• Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) – NIFTP is a non-cancerous type of thyroid tumour. The tumour cells are separated from the normal thyroid gland by a thin tissue barrier called a capsule.
• Follicular variant of papillary thyroid carcinoma – Follicular variant of papillary thyroid carcinoma is a type of thyroid cancer. Most tumours are at least partially separated from the normal thyroid gland by a thin barrier called a capsule. The cells in a follicular variant of papillary thyroid carcinoma look similar to the cells in an NIFTP. The most important difference is that in follicular variant papillary thyroid carcinoma, the tumour cells cross the capsule and spread into the surrounding thyroid gland.

In order to determine which of these conditions you have, all the abnormal tissue needs to be removed and examined under a microscope. In particular, the pathologist needs to be able to determine if the abnormal growth is surrounded by a capsule and if the cells inside the growth have crossed the capsule into the surrounding thyroid gland. This examination can only be performed after the entire tumour is removed. Look for the final diagnosis in your pathology report after the tumour is removed.

Is a follicular neoplasm a cancer?

Not necessarily. Follicular neoplasm is a general term used to describe a group of non-cancerous and cancerous conditions that look similar when only a small part piece of tissue is examined under the microscope.

How is the diagnosis “suspicious for follicular neoplasm” made?

This diagnosis is usually made after a procedure called a fine needle aspiration biopsy (FNAB). Rarely, this diagnosis is made after the entire growth has been removed along with the surrounding thyroid lobe.

When examined under the microscope, the cells in the tissue sample will look similar to the follicular cells that are normally found in the thyroid gland. The cells usually stick together to form round structures called follicles. However, the follicles in the sample are often smaller than normal follicles. As a result, they are often described as microfollicles. The follicular cells may also be arranged in small groups or even as single-detached cells. Your pathologist may use the term atypical to describe cells that have an abnormal shape, colour, or size compared to normal, healthy, follicular cells. Cells may become atypical as a result of cancer, infection, radiation, medications, or inflammation.