What are the different subtypes and its response to RAI

Reading File

Finding Sources

Searching PubMed

"thyroid neoplasms"[MeSH Terms] AND radioiodine

Searching the Web

2025 ATA differentiated thyroid cancer radioiodine therapy histologic subtype uptake guidance

Reading File

Finding Sources

Reading Web Page

https://www.thyroid.org/patient-thyroid-information/ct-for-p…

Assuming you mean thyroid carcinoma subtypes and their response to radioactive iodine (RAI, I-131):

RAI works only when tumor cells retain thyroid-cell differentiation and sodium-iodide transporter activity. Thus, differentiated thyroid cancers (DTC) are usually RAI-avid, while medullary and anaplastic cancers are not.

Histologic subtype	Expected RAI response	Key point
Classic papillary thyroid carcinoma (PTC)	Usually good	Most common DTC. RAI can treat residual, nodal, or distant iodine-avid disease, but is not routinely needed in low-risk small tumors.
Follicular variant PTC, encapsulated/invasive	Usually good	Often behaves similarly to follicular-pattern DTC.
Follicular thyroid carcinoma (FTC)	Good, especially distant metastases	Bone and lung metastases can be iodine-avid and may respond well.
Oncocytic thyroid carcinoma (Hürthle-cell carcinoma)	Often poor	Lower RAI avidity than conventional papillary or follicular cancers, so benefit is less reliable.
Tall-cell PTC	Variable, often reduced	An aggressive PTC subtype. Some lesions take up RAI, but recurrence and RAI-refractory disease are more frequent than in classic PTC.
Hobnail PTC	Often poor	Aggressive subtype with a higher likelihood of RAI refractoriness.
Columnar-cell PTC	Variable to poor	Aggressive behavior; RAI benefit is less predictable.
Diffuse sclerosing PTC	Often RAI-avid	Frequently presents with extensive nodal/pulmonary disease, but can still respond to RAI.
Solid/trabecular PTC	Variable	Can be iodine-avid, but behavior depends on age, invasion, mutations, and metastatic pattern.
Poorly differentiated thyroid carcinoma	Variable, commonly limited	May retain partial uptake, but loss of differentiation often reduces effectiveness.
Anaplastic thyroid carcinoma	Essentially no meaningful response	Usually lacks iodine uptake. Treatment relies on urgent local control, molecular testing, targeted therapy when appropriate, radiation, and systemic therapy.
Medullary thyroid carcinoma	No response	Derived from parafollicular C cells, not follicular cells, so it does not concentrate iodine.
NIFTP	RAI not indicated	Noninvasive follicular thyroid neoplasm with papillary-like nuclear features is not managed as invasive thyroid cancer.

Practical summary

Best RAI responders: classic PTC, follicular-variant PTC, and FTC.
Less reliable responders: tall-cell, hobnail, columnar-cell, poorly differentiated, and oncocytic/Hürthle-cell carcinomas.
Do not respond: medullary and anaplastic carcinoma.
RAI is not automatically given because a tumor is PTC or FTC. The decision depends mainly on postoperative recurrence risk, tumor size, extrathyroidal extension, vascular invasion, nodal/distant metastases, postoperative thyroglobulin, and iodine imaging. The 2025 ATA framework specifically uses pathology and recurrence risk to identify patients likely to benefit from additional therapy such as RAI, as summarized by the American Thyroid Association.

RAI-refractory disease

A differentiated thyroid cancer is considered RAI-refractory if, for example:

Metastases never take up RAI.
Previously iodine-avid lesions lose uptake over time.
Some lesions take up iodine but others do not.
Disease progresses despite meaningful iodine uptake and adequately delivered RAI.

In this setting, repeating RAI rarely helps. Management may shift to surveillance for indolent disease, surgery or focal therapy for isolated lesions, external-beam radiotherapy in selected cases, or mutation-directed/systemic therapies.

Recent evidence also supports avoiding routine RAI in many low-risk DTC cases after surgery, rather than deciding by subtype alone. See the 2025 pooled trial analysis and systematic review.

focus on papillary thyroid cancer, and the percentage of r

Reading File

Do you mean the percentage of papillary thyroid cancers that are RAI-avid / respond to radioactive iodine, or the percentage risk of recurrence for each papillary subtype?

different subtypes of PTC and their response to RAI

Reading File

Finding Sources

Searching PubMed

"papillary thyroid carcinoma" AND radioiodine

Searching the Web

papillary thyroid carcinoma variants radioactive iodine avidity tall cell diffuse sclerosing hobnail columnar cell systematic review

Searching PubMed

"tall cell variant" AND radioiodine

Searching PubMed

"hobnail variant" AND radioiodine

Searching PubMed

"diffuse sclerosing" AND radioiodine

Reading Web Page

https://pmc.ncbi.nlm.nih.gov/articles/PMC8307105

Papillary thyroid carcinoma (PTC) subtypes and response to radioactive iodine (RAI)

Important: there is no single reliable “response percentage” for every PTC subtype. RAI response depends not only on histology, but also on metastatic site and burden, completeness of surgery, TSH stimulation, iodine uptake on scan, age, and molecular profile, especially BRAF V600E and TERT-promoter mutations.

PTC subtype	Typical RAI avidity / expected response	Clinical interpretation
Classic (conventional) PTC	Usually RAI-avid and responsive when RAI is indicated	This is the reference favorable subtype. Most low-risk, intrathyroidal tumors do not need RAI at all.
Follicular variant PTC	Usually good avidity	Generally has a favorable response profile, particularly encapsulated forms without invasion.
Warthin-like PTC	Usually favorable	Behaves more like classic PTC and is generally not considered an RAI-resistant subtype.
Diffuse sclerosing variant (DSV)	Often RAI-avid, but clinically aggressive	Frequently has extensive nodal disease and sometimes lung metastases. In one cohort, post-treatment RAI uptake was seen in 33% (24/72) of nodal metastases and 80% (4/5) of distant metastases. Thus, it may respond to RAI despite its higher recurrence risk.
Tall-cell variant (TCV)	Reduced avidity and higher risk of RAI-refractory disease	Often BRAF-driven, with more extrathyroidal extension and nodal/distant spread. RAI can be used if lesions are avid, but response is less dependable than for classic PTC.
Hobnail variant	Frequently poor avidity / less reliable response	A rare aggressive subtype. Has a higher likelihood of persistent, recurrent, and RAI-refractory disease.
Columnar-cell variant	Variable but often reduced response	Aggressive histology. RAI may be given for appropriate risk features, but uptake and durable response are inconsistent.
Solid/trabecular variant	Variable	May be iodine-avid, especially in younger patients, but is treated as an aggressive histologic subtype when other high-risk features are present.
Oncocytic PTC	Often reduced avidity	Oxyphilic/oncocytic change is associated with lower iodine avidity and a less dependable therapeutic response.
PTC with poorly differentiated/high-grade features	Often poor response	Dedifferentiation reduces sodium-iodide transporter expression and therefore iodine uptake.

Best way to remember it

Favorable RAI pattern: classic PTC, follicular-variant PTC, Warthin-like PTC.
Can still be RAI-avid despite aggressive behavior: diffuse sclerosing PTC.
Greater risk of low uptake or RAI-refractoriness: tall-cell, hobnail, columnar-cell, solid/trabecular, and oncocytic PTC.

A tissue-based study grouped classic, follicular-variant, diffuse-sclerosing, and Warthin-like PTC as relatively favorable for iodine avidity. Tall-cell, hobnail, and oxyphilic PTC had mean iodine avidity 10.4-fold lower than that favorable group, though the confidence interval was wide because these are rare tumors. See the iodine-avidity study.

Risk of becoming RAI-refractory

A meta-analysis found that having a high-risk histologic subtype, including tall-cell, diffuse-sclerosing, or hobnail PTC, was associated with increased odds of RAI-refractory differentiated thyroid cancer: odds ratio 1.94 (95% CI 1.15-3.27). The risk is further increased by:

BRAF V600E mutation: OR 3.60
TERT-promoter mutation: OR 9.84
Extrathyroidal extension: OR 2.28

These figures estimate the risk of RAI refractoriness, not the percentage that will respond to a dose of RAI. See the meta-analysis.

Practical implication

Histology alone should not decide RAI treatment. RAI is more appropriate when there is substantial residual disease, nodal disease with adverse features, vascular invasion, gross extrathyroidal extension, or iodine-avid distant metastasis. The 2025 ATA approach incorporates PTC subtype along with all of these risk features when deciding who is likely to benefit from RAI, as summarized by the ATA guideline update.

Relate it to this patient 77/f B) Thyroid Gland (304 Grams): - MULTIFOCAL PAPILLARY THYROID CARCINOMA: > TALL CELL SUBTYPE, LEFT LOBE (8 CM.). > CLASSIC/CONVENTIONAL, RIGHT LOBE (2.1 CM. AND 0.2 CM.) > INFILTRATIVE FOLLICULAR SUBTYPE, RIGHT LOBE (1.3 CM. AND 0.1 CM.) AND ISTHMUS (0.2 CM.) - EXTRATHYROIDAL EXTENSION TO SKELETAL MUSCLE: NOT IDENTIFIED. - LYMPHOVASCULAR INVASION: PRESENT. - PERINEURAL INVASION: NOT IDENTIFIED. - TUMOR NECROSIS: PRESENT. - MITOTIC ACTIVITY: LESS THAN 3 PER 2 MM2. - MARGINS, NEGATIVE FOR CARCINOMA. > TUMOR IS WITHIN 1 MM. OF INKED ANTERIOR AND POSTERIOR MARGINS. - INTERNAL JUGULAR VEIN: NEGATIVE FOR CARCINOMA.

I can map the pathology to recurrence risk, staging, expected RAI responsiveness, and next-treatment implications.

Asking for Preferences

Which aspect should I analyze in detail first?

Assuming you mean thyroid carcinoma subtypes and their response to radioactive iodine (RAI, I-131):

Histologic subtype	Expected RAI response	Key point
Classic papillary thyroid carcinoma (PTC)	Usually good	Most common DTC. RAI can treat residual, nodal, or distant iodine-avid disease, but is not routinely needed in low-risk small tumors.
Follicular variant PTC, encapsulated/invasive	Usually good	Often behaves similarly to follicular-pattern DTC.
Follicular thyroid carcinoma (FTC)	Good, especially distant metastases	Bone and lung metastases can be iodine-avid and may respond well.
Oncocytic thyroid carcinoma (Hürthle-cell carcinoma)	Often poor	Lower RAI avidity than conventional papillary or follicular cancers, so benefit is less reliable.
Tall-cell PTC	Variable, often reduced	An aggressive PTC subtype. Some lesions take up RAI, but recurrence and RAI-refractory disease are more frequent than in classic PTC.
Hobnail PTC	Often poor	Aggressive subtype with a higher likelihood of RAI refractoriness.
Columnar-cell PTC	Variable to poor	Aggressive behavior; RAI benefit is less predictable.
Diffuse sclerosing PTC	Often RAI-avid	Frequently presents with extensive nodal/pulmonary disease, but can still respond to RAI.
Solid/trabecular PTC	Variable	Can be iodine-avid, but behavior depends on age, invasion, mutations, and metastatic pattern.
Poorly differentiated thyroid carcinoma	Variable, commonly limited	May retain partial uptake, but loss of differentiation often reduces effectiveness.
Anaplastic thyroid carcinoma	Essentially no meaningful response	Usually lacks iodine uptake. Treatment relies on urgent local control, molecular testing, targeted therapy when appropriate, radiation, and systemic therapy.
Medullary thyroid carcinoma	No response	Derived from parafollicular C cells, not follicular cells, so it does not concentrate iodine.
NIFTP	RAI not indicated	Noninvasive follicular thyroid neoplasm with papillary-like nuclear features is not managed as invasive thyroid cancer.

Practical summary

Best RAI responders: classic PTC, follicular-variant PTC, and FTC.
Less reliable responders: tall-cell, hobnail, columnar-cell, poorly differentiated, and oncocytic/Hürthle-cell carcinomas.
Do not respond: medullary and anaplastic carcinoma.
RAI is not automatically given because a tumor is PTC or FTC. The decision depends mainly on postoperative recurrence risk, tumor size, extrathyroidal extension, vascular invasion, nodal/distant metastases, postoperative thyroglobulin, and iodine imaging. The 2025 ATA framework specifically uses pathology and recurrence risk to identify patients likely to benefit from additional therapy such as RAI, as summarized by the American Thyroid Association.

RAI-refractory disease

A differentiated thyroid cancer is considered RAI-refractory if, for example:

Metastases never take up RAI.
Previously iodine-avid lesions lose uptake over time.
Some lesions take up iodine but others do not.
Disease progresses despite meaningful iodine uptake and adequately delivered RAI.

Recent evidence also supports avoiding routine RAI in many low-risk DTC cases after surgery, rather than deciding by subtype alone. See the 2025 pooled trial analysis and systematic review.Do you mean the percentage of papillary thyroid cancers that are RAI-avid / respond to radioactive iodine, or the percentage risk of recurrence for each papillary subtype?## Papillary thyroid carcinoma (PTC) subtypes and response to radioactive iodine (RAI)

PTC subtype	Typical RAI avidity / expected response	Clinical interpretation
Classic (conventional) PTC	Usually RAI-avid and responsive when RAI is indicated	This is the reference favorable subtype. Most low-risk, intrathyroidal tumors do not need RAI at all.
Follicular variant PTC	Usually good avidity	Generally has a favorable response profile, particularly encapsulated forms without invasion.
Warthin-like PTC	Usually favorable	Behaves more like classic PTC and is generally not considered an RAI-resistant subtype.
Diffuse sclerosing variant (DSV)	Often RAI-avid, but clinically aggressive	Frequently has extensive nodal disease and sometimes lung metastases. In one cohort, post-treatment RAI uptake was seen in 33% (24/72) of nodal metastases and 80% (4/5) of distant metastases. Thus, it may respond to RAI despite its higher recurrence risk.
Tall-cell variant (TCV)	Reduced avidity and higher risk of RAI-refractory disease	Often BRAF-driven, with more extrathyroidal extension and nodal/distant spread. RAI can be used if lesions are avid, but response is less dependable than for classic PTC.
Hobnail variant	Frequently poor avidity / less reliable response	A rare aggressive subtype. Has a higher likelihood of persistent, recurrent, and RAI-refractory disease.
Columnar-cell variant	Variable but often reduced response	Aggressive histology. RAI may be given for appropriate risk features, but uptake and durable response are inconsistent.
Solid/trabecular variant	Variable	May be iodine-avid, especially in younger patients, but is treated as an aggressive histologic subtype when other high-risk features are present.
Oncocytic PTC	Often reduced avidity	Oxyphilic/oncocytic change is associated with lower iodine avidity and a less dependable therapeutic response.
PTC with poorly differentiated/high-grade features	Often poor response	Dedifferentiation reduces sodium-iodide transporter expression and therefore iodine uptake.

Best way to remember it

Favorable RAI pattern: classic PTC, follicular-variant PTC, Warthin-like PTC.
Can still be RAI-avid despite aggressive behavior: diffuse sclerosing PTC.
Greater risk of low uptake or RAI-refractoriness: tall-cell, hobnail, columnar-cell, solid/trabecular, and oncocytic PTC.

Risk of becoming RAI-refractory

BRAF V600E mutation: OR 3.60
TERT-promoter mutation: OR 9.84
Extrathyroidal extension: OR 2.28

These figures estimate the risk of RAI refractoriness, not the percentage that will respond to a dose of RAI. See the meta-analysis.

Practical implication

Recent evidence supports the association between BRAF mutation and poorer RAI outcomes in PTC, but this should be interpreted with pathology and imaging rather than used alone. See the 2025 systematic review and meta-analysis.I can map the pathology to recurrence risk, staging, expected RAI responsiveness, and next-treatment implications.

Reading File

Finding Sources

Searching PubMed

"papillary thyroid carcinoma" AND radioiodine

Searching the Web

2025 ATA differentiated thyroid cancer tall cell variant vascular invasion RAI recommendation

How this pathology relates to RAI

This is multifocal papillary thyroid carcinoma (PTC) with three histologic patterns, dominated by a large 8 cm tall-cell PTC in the left lobe.

The tall-cell component is the clinically dominant subtype because it is the largest lesion and is an aggressive PTC variant. In practice, risk assessment and the expected response to radioactive iodine (RAI, I-131) should be based mainly on that dominant 8 cm tall-cell tumor and its adverse features, rather than on the smaller classic and infiltrative follicular-variant foci.

Finding	Meaning for this patient
Tall-cell PTC, 8 cm	Aggressive histology. Compared with classic PTC, it has a greater chance of lower iodine avidity, recurrence, and RAI-refractory disease. RAI can still work if metastatic or residual tumor takes up iodine.
Classic PTC, 2.1 cm and 0.2 cm	Usually iodine-avid and generally more RAI-responsive, but these smaller foci do not offset the risk from the tall-cell primary.
Infiltrative follicular-variant PTC, up to 1.3 cm	Often retains iodine uptake, but “infiltrative” distinguishes it from the more indolent encapsulated pattern. It reinforces the multifocal nature of disease.
Multifocal, bilateral disease	Supports total thyroidectomy and makes postoperative thyroglobulin monitoring and RAI-based evaluation more useful.
Lymphovascular invasion present	Indicates access to lymphatic/blood vessels and increases concern for nodal or distant microscopic spread. It is an adverse recurrence-risk feature and supports considering adjuvant RAI.
Tumor necrosis present	An adverse biologic feature. With the tall-cell morphology, it raises concern for less differentiated behavior and lower odds of a durable RAI response.
No gross extrathyroidal extension into skeletal muscle	Favorable. There is no documented invasion outside the thyroid, which reduces local-risk severity.
Margins negative, but <1 mm anterior/posterior	This is still an R0 resection, meaning no tumor at the cut edge. A close negative margin does not equal residual cancer, but it supports careful surveillance.
Internal jugular vein negative	Favorable, with no documented major venous invasion.

Pathologic stage

Assuming the 8 cm tumor is confined to the thyroid, as stated:

Primary tumor: pT3a because it is >4 cm and there is no gross extrathyroidal extension.
Nodal category: pN cannot be assigned from the provided report because no lymph-node findings are included. If no nodes were removed, this is pNx.
Distant metastasis: cannot be assigned pathologically. It requires imaging and clinical evaluation.

For a patient aged 77, if imaging shows no distant metastasis, a T3a PTC is generally AJCC 8th edition Stage II, regardless of whether regional nodes are involved. Stage here predicts mortality risk, whereas ATA recurrence-risk stratification guides RAI and surveillance decisions.

Recurrence-risk category

Using the conventional ATA framework, she is at least intermediate risk of recurrence, chiefly because of:

Tall-cell histology
Lymphovascular invasion
Large primary tumor
Multifocal bilateral disease

She is not automatically ATA high risk from the report alone, because the report does not show gross extrathyroidal extension, gross residual tumor, or distant metastasis. However, the actual category may escalate if there are bulky lymph nodes, extranodal extension, distant metastases, or high-risk molecular findings.

Textbook risk tables specifically list aggressive histology such as tall-cell PTC and vascular invasion as features outside the low-risk group. Schwartz's Principles of Surgery, 11th ed., postoperative management of differentiated thyroid cancer.

What this means for RAI response

Likelihood of RAI being recommended

Adjuvant RAI would usually be strongly considered in this case, assuming the patient has undergone total thyroidectomy and has adequate renal function and no contraindication. The purpose would be to:

Treat possible microscopic iodine-avid residual disease.
Detect occult nodal or distant disease on post-therapy scanning.
Improve the interpretability of follow-up thyroglobulin testing.

This is very different from a small, unifocal, classic low-risk PTC where RAI is often omitted.

Likelihood of RAI working

The accurate answer is unknown until post-treatment uptake imaging and follow-up thyroglobulin are available.

The classic and follicular-variant foci are relatively more likely to retain iodine uptake.
The dominant tall-cell tumor has a higher probability of weak uptake or eventual RAI-refractory behavior than classic PTC.
That does not mean it is RAI-refractory now. Many tall-cell cancers and their metastases still take up I-131 and can respond.

It would be misleading to give a single response percentage for this patient from pathology alone. A study comparing PTC variants found that a group including tall-cell, hobnail, and oxyphilic tumors had mean iodine avidity 10.4-fold lower than the group containing conventional, follicular-variant, diffuse-sclerosing, and Warthin-like PTC, but this was a small tissue-based study and does not predict an individual patient’s response. See the iodine-avidity study.

A meta-analysis also found that high-risk histology, including tall-cell PTC, was associated with greater odds of radioiodine-refractory differentiated thyroid cancer, but this is a risk association, not proof of resistance in an individual patient. See the RAI-refractory disease meta-analysis.

High-yield next steps to clarify RAI benefit

Review the neck-dissection pathology, if performed: number of positive nodes, largest metastasis, and extranodal extension.
Postoperative thyroglobulin and anti-thyroglobulin antibodies, ideally interpreted with TSH status.
High-resolution neck ultrasound.
Cross-sectional chest imaging, often CT chest, because an 8 cm tall-cell tumor with lymphovascular invasion warrants attention to possible pulmonary metastases.
Post-therapy I-131 whole-body scan with SPECT/CT if RAI is given. This is the direct test of whether residual or metastatic disease is iodine-avid.
Molecular testing, particularly BRAF V600E and TERT-promoter mutations. Their coexistence would increase concern for recurrence and RAI-refractory disease. A recent systematic review supports an association between BRAF mutation and poorer RAI outcomes, though molecular results must be interpreted alongside imaging and pathology. See the 2025 meta-analysis.

Finally, TSH suppression is often used after treatment in an intermediate-risk patient, but in a 77-year-old, the target must be balanced against atrial fibrillation, ischemic heart disease, and bone-loss risk. This should be individualized by endocrinology and the thyroid cancer multidisciplinary team.

Can you make it into a paragraph discussing the different subtypes of PTC at its response to RAI and in relation to this patients case

Reading File

Papillary thyroid carcinoma (PTC) comprises several histologic subtypes with differing biologic behavior and response to radioactive iodine (RAI). Classic/conventional PTC and follicular-variant PTC usually retain thyroid-cell differentiation and are therefore more likely to concentrate iodine and respond to RAI when treatment is indicated. In contrast, aggressive variants, particularly tall-cell, hobnail, columnar-cell, solid/trabecular, and oncocytic PTC, more often show reduced iodine avidity and a greater risk of persistent or recurrent RAI-refractory disease. Diffuse sclerosing PTC is also an aggressive subtype with frequent nodal and occasional pulmonary involvement, but it may still demonstrate meaningful RAI uptake. In this 77-year-old patient, the dominant lesion is an 8 cm tall-cell PTC, while smaller conventional and infiltrative follicular-variant PTC foci are present in the contralateral lobe and isthmus. Although the conventional and follicular-variant components are relatively more likely to be RAI-avid, the overall risk profile and anticipated RAI response are driven primarily by the large tall-cell carcinoma. Its large size, multifocal bilateral disease, lymphovascular invasion, and tumor necrosis support at least an intermediate recurrence risk and make adjuvant RAI a reasonable consideration after total thyroidectomy, provided there is no contraindication. However, tall-cell histology carries a higher likelihood of reduced iodine uptake than conventional PTC, so RAI effectiveness cannot be predicted from pathology alone. The post-therapy I-131 whole-body scan, preferably with SPECT/CT, together with postoperative thyroglobulin and anti-thyroglobulin antibody levels, will determine whether residual or metastatic disease is iodine-avid and whether RAI is likely to provide therapeutic benefit.

This is a shared conversation. Sign in to Orris to start your own chat.