BACKGROUND
Papillary thyroid cancer is the most common type of thyroid cancer and, overall, the prognosis is excellent. This is because papillary thyroid cancer grows very slowly and we have very effective treatments (surgery and, if needed, radioactive iodine). One type of papillary thyroid cancer, known as noninvasive encapsulated follicular variant of papillary thyroid carcinoma (FVPTC), rarely spread outside of the thyroid. A study showed that no recurrence after surgery after at least 10 years of follow-up of 109 patients diagnosed with noninvasive encapsulated FVPTC.

In 2016, an international group of experts suggested that noninvasive encapsulated FVPTC was not a cancer at all and more consistent with a precancerous neoplasm (growth). They proposed to change the name to noninvasive thyroid follicular neoplasm with papillary-like nuclear features (NIFTP). The World Health Organization recognized NIFTP as a new term in 2017. The downgrade of the NIFTP category from carcinoma to a low-risk neoplasm was performed to reduce overtreatment of these tumors. The long-term outcome of NIFTP is still being investigated. The goal of this study was to analyze a large group of NIFTP patients diagnosed at a single institution since the introduction of this term in 2016 and further stratify and compare the pure NIFTP patients with those who had other co-existing low-risk and high-risk thyroid cancers.

THE FULL ARTICLE TITLE
Alzumaili BA 2023 A Comprehensive Study on the Diagnosis and Management of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features. Thyroid 33:566–577. PMID: 36960710.

SUMMARY OF THE STUDY
The study included 319 patients diagnosed with NIFTP between 2016 and 2022 identified through the Massachusetts General Hospital Laboratory Information database. The patients were divided into three groups: (1) NIFTP-only (183 patients); (2) NIFTP with one concomitant low risk papillary thyroid microcarcinoma (53 patients); and (3) NIFTP with a concomitant high risk thyroid carcinoma, defined as 2 or more microcarcinomas, any papillary thyroid carcinoma larger than 1.0 cm, any follicular or medullary thyroid carcinoma, or any thyroid cancer with spread to the neck lymph nodes (83 patients). In group 3, 15 (19%) patients with papillary thyroid cancer had spread to the neck lymph nodes.

Among all study patients, 73 patients (23%) had multiple thyroid nodules and 39 (12%) had multiple foci of NIFTP. A total of 256 (80%) of the thyroid nodules diagnosed as NIFTP after surgery underwent fine-needle aspiration (FNA) prior to the thyroid surgery with the following cytologic results: 12 patients (5%) non-diagnostic (Bethesda I), 34 patients (13%) benign (Bethesda II), 125 patients (49%) atypia of undetermined significance (Bethesda III), 43 patients (17%) follicular neoplasm (Bethesda IV), 32 patients (12%) suspicious for malignancy (Bethesda V), and 10 patients (4%) malignant (Bethesda VI). A total of 106 patients of the 114 patients who had molecular tests (93%) showed molecular alterations, the majority being RAS mutations (49 patients), with NRAS p.Q61R being the most common (32 patients).

Overall 66% of patients in group 1, 49% of patients in group 2, and 28% of patients in group 3 underwent a lobectomy. None of the patients who underwent initial lobectomy required treatment with completion thyroidectomy or radioactive iodine in group 1 and 2. In group 3, 6 out of 23 patients who underwent lobectomy required subsequent completion thyroidectomy, while 19 patients underwent radioactive iodine ablation. In group 1, follow-up neck ultrasound was performed in 28% of patients (52 patients). No recurrences or metastases were diagnosed within an average follow-up of 35 months (range 6–76 months) in group 1 and 45 months (range 8–77) in group 2. In group 3, 1 patient was diagnosed with neck lymph node cancer recurrence 8 months after surgery. All patients in group 3 were disease-free and there were no disease-specific deaths during an average follow-up of 46 months (range 6–77).

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
The results of this study evaluating a large group from a single medical center support the notion that isolated NIFTP is benign. The authors propose that patients with an isolated NIFTP should have clinical follow-up similar to a benign nodule and that the treatment of patients with NIFTP and concomitant thyroid cancers should be based on the non-NIFTP cancer. Additional long-term studies are needed to better define the best surgical approach and postoperative followup for patients diagnosed with NIFTP.

— Alina Gavrila, MD, MMSC

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