# Follicular thyroid cancer

Source: https://onco.cc/cancers/follicular-thyroid-cancer/  
OnCo record `follicular-thyroid-cancer` (Cancer). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Follicular thyroid cancer looks like a benign nodule on a needle biopsy, so the diagnosis is usually made only after surgery. It spreads through the bloodstream rather than to neck nodes, is treated like papillary cancer with surgery and radioactive iodine, and has a good outlook when caught early.

## Summary

Follicular thyroid cancer is separated from a benign follicular adenoma only by invasion of the capsule or blood vessels, which a fine-needle biopsy cannot show; a follicular result on biopsy therefore leads to diagnostic lobectomy, and molecular tests on the aspirate now help decide who needs it. RAS mutations and the PAX8-PPARG fusion are common, and TERT promoter mutations mark aggressive disease. Minimally invasive tumours are cured by lobectomy; widely invasive tumours receive total thyroidectomy and radioactive iodine, which also treats the lung and bone metastases the disease favours. Oncocytic (Hurthle cell) carcinoma, once a follicular variant, is a separate entity in the 2022 WHO classification and takes up iodine poorly. Iodine-refractory disease is treated as in papillary cancer with lenvatinib or sorafenib.

## Fields

- Kind: Cancer
- Last checked: 2026-09-17
- Also known as: Follicular thyroid carcinoma; FTC; Oncocytic (Hurthle cell) carcinoma
- Tags: subtype-page
- Group: endocrine
- Burden: About one in ten thyroid cancers, commoner where iodine is scarce; it spreads through the blood to bone and lung rather than to neck nodes, and survival is somewhat lower than for papillary cancer but still high.
- Subtypes: Minimally invasive (capsular invasion only); Encapsulated angioinvasive; Widely invasive; Oncocytic (Hurthle cell) carcinoma (separate entity since WHO 2022)
- Biomarkers: RAS mutations; PAX8-PPARG fusion; TERT promoter mutation; Molecular tests on indeterminate aspirates (Afirma, ThyroSeq); Thyroglobulin

## Standard of care

- Indeterminate follicular nodule: Molecular testing of the aspirate; diagnostic lobectomy when suspicious. ([Thyroid cancer](https://onco.cc/cancers/thyroid/))
- Minimally invasive: Lobectomy alone in most cases; completion surgery and iodine only for high-risk features. ([Thyroid cancer](https://onco.cc/cancers/thyroid/))
- Widely invasive or metastatic: Total thyroidectomy, radioactive iodine, TSH suppression; bone metastases may need surgery or radiotherapy. ([Radioiodine therapy and whole-body iodine scanning](https://onco.cc/technologies/radioiodine-therapy/), [Palliative radiotherapy](https://onco.cc/technologies/palliative-radiotherapy/))
- Iodine-refractory: Lenvatinib or sorafenib; clinical trials of redifferentiation. ([Lenvatinib](https://onco.cc/drugs/lenvatinib/), [Sorafenib](https://onco.cc/drugs/sorafenib/), [Radioiodine-refractory (RAI-R) thyroid cancer](https://onco.cc/terms/rai-refractory/))

## State of the art

- Molecular testing of indeterminate nodules spares many patients a diagnostic operation.
- Most follicular cancers are cured by surgery alone; the widely invasive minority drives the deaths.
- Oncocytic carcinoma's separation as its own entity reflects its distinct genetics and poor iodine avidity.

## Open problems

- Telling adenoma from carcinoma without surgery.
- Bone metastases respond poorly to iodine.
- Few trials specific to follicular histology.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Follicular_thyroid_cancer
- Wikipedia: https://en.wikipedia.org/wiki/Follicular_thyroid_cancer

## Connected records

- technologies: [Palliative radiotherapy](https://onco.cc/technologies/palliative-radiotherapy/), [Radioiodine therapy and whole-body iodine scanning](https://onco.cc/technologies/radioiodine-therapy/)
- drugs: [Dabrafenib](https://onco.cc/drugs/dabrafenib/), [Lenvatinib](https://onco.cc/drugs/lenvatinib/), [Sorafenib](https://onco.cc/drugs/sorafenib/)
- cancers: [Thyroid cancer](https://onco.cc/cancers/thyroid/)
- terms: [Radioiodine-refractory (RAI-R) thyroid cancer](https://onco.cc/terms/rai-refractory/)

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