Metastatic papillary thyroid carcinoma vs ectopic thyroid inclusion...

[cmz]

I had a recent case that came to me as a core needle biopsy specimen of an "enlarged supraclavicular mass/node" in an elderly lady with a remote history of papillary thyroid CA (and complete thyroidectomy performed). I have bits and fragments of bland-appearing thyroid epithelium with no cytologic evidence for papillary CA. In addition, there is no distinct evidence that a lymph node was actually sampled (it's just pure thyroid parenchyma ... which stayed the same after a couple of deeper sections).

Would you call this malignant even though the cytology doesn't agree with that statement? Is it possible that there could be some remnant benign heterotopic thyroid tissue? Recommend that this lady be subjected to an excisional biopsy to fully characterize what's going on?

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[cmz]

... but just on a side note, I've read that ectopic benign thyroid tissue doesn't exist. It should always be called malignant.

 

[Ziehl-Neelsen]

Would you call this malignant even though the cytology doesn't agree with that statement?

0% chance I would call it malignant on the biopsy based on what you've described. The histologic diagnosis of PTC is based on nuclear and cytologic features with supportive architectural features. There are so many benign mimics that are within the realm of possibility (parastitic nodule, retrosternal thyroid, heterotopic thyroid due to aberrant embryonal migration, pyramidal lobe missed on the initial thyroidectomy, etc.).

I'd absolutely recommend that the lesion be resected for complete characterization.

 

[cmz]

I favor being conservative for the reasons you mentioned.; however, I did forget to mention that the sampled "supraclavicular node/mass" measures 2.8 cm. It's either a big LN or a small to normal-sized thyroid lobe. I guess I just find it odd that this was supposedly sampled from an area of the neck away from the midline in a patient with no thyroid (though incomplete resection is always in the back of my mind).

I've also read that metastatic papillary thyroid CA to nodes (though, this isn't exactly proven in my case) is often histologically bland appearing. Again, I have no way of saying this was sampled from a node. At this point, I find making a preemptive phone call to the clinician always helps

I know that I could order a few IHCs and/or send off for BRAF mutation... but the tissue is so scanty and it seems like a huge waste of money to do so...

 

[coroner]

... but just on a side note, I've read that ectopic benign thyroid tissue doesn't exist. It should always be called malignant.

???

1) Thyroid gland - Heterotopic tissue
2) Ectopic thyroid tissue: anatomical, clinical, and surgical implications of a rare entity
3) Imaging of Ectopic Thyroid Tissue and Thyroglossal Duct Cysts

 

[cmz]

???

1) Thyroid gland - Heterotopic tissue
2) Ectopic thyroid tissue: anatomical, clinical, and surgical implications of a rare entity
3) Imaging of Ectopic Thyroid Tissue and Thyroglossal Duct Cysts

I misspoke about saying "ectopic"... too much multitasking I really meant to only mention the concept of "benign thyroid tissue in lymph nodes" doesn't really exist according to some experts. Thanks!

The case was signed out as "benign" with a recommendation for excision.

 

[tiredguy]

i had a case like this, except a young woman with no h/o PTC and an FNA was also performed. the core bx looked bland and thyroid expert agreed, but the FNA had some nuclear atypia. no lymphoid tissue. on excision it turned out to be metastatic PTC.

 

[cmz]

i had a case like this, except a young woman with no h/o PTC and an FNA was also performed. the core bx looked bland and thyroid expert agreed, but the FNA had some nuclear atypia. no lymphoid tissue. on excision it turned out to be metastatic PTC.

Was this a core biopsy of a LN (or something designated as such)?

 

[schrute]

1. I'd be sure they sampled the SCN as opposed to some lateral neck lesion...but even a 2.8 cm portion of thyroidal tissue in a patient who has allegedly undergone a total thyroidectomy for PTC suggests something is amiss (2.8 cm heterotopic foci just don't 'pop up').
2. I've seen several PTC nodal mets (and organ mets) that look bland as hell--wouldn't worry too much about the cytology.
3. Wouldn't top-line it as 'benign'...closest I'd be is 'benign appearing' but given the history, raises suspicion for metastatic disease.
would like to see what the neck imaging showed.

 

[tiredguy]

Was this a core biopsy of a LN (or something designated as such)?

they didn't know what it was but were not expecting a lymph node. for whatever reason radiology was guessing it to be a schwannoma. there was a subsequent FNA of a thyroid nodule that ended up being PTC prior to the neck mass excision.

 

[27G]

There are IHC profiles that can help with this. http://ajcp.ascpjournals.org/content/126/5/700.full.pdf
I do however think it is very important to have the "lesion", mass removed. Were there ultrasound findings suggestive of lymph node? Statistically benign thyroid parynchema in the vacinity of the SC LN could be an ectopic rest or possibly a developmental anomaly such as a thyroductal duct cyst. If you have the IHC's available in the link above I would do them. Some labs do the BRAF and other studies that would be absent in benign thyroid tissue as well. I would not top line this as malignant but give the diagnosis like: "thyroid tissue present" and a comment with a differential and a request for excisional biopsy for further workup. Definitely mention that although the biopsy site is designated as lymph node, the absence of lymphocytes precludes optimal biopsy site assessment. Follicular variant of PTC can be challenging and follicular carcinoma although a possibility does not usually spread through lymphatics but hematogenously.

 

[cmz]

There are IHC profiles that can help with this. http://ajcp.ascpjournals.org/content/126/5/700.full.pdf
I do however think it is very important to have the "lesion", mass removed. Were there ultrasound findings suggestive of lymph node? Statistically benign thyroid parynchema in the vacinity of the SC LN could be an ectopic rest or possibly a developmental anomaly such as a thyroductal duct cyst. If you have the IHC's available in the link above I would do them. Some labs do the BRAF and other studies that would be absent in benign thyroid tissue as well. I would not top line this as malignant but give the diagnosis like: "thyroid tissue present" and a comment with a differential and a request for excisional biopsy for further workup. Definitely mention that although the biopsy site is designated as lymph node, the absence of lymphocytes precludes optimal biopsy site assessment. Follicular variant of PTC can be challenging and follicular carcinoma although a possibility does not usually spread through lymphatics but hematogenously.

I expressed the need for this mass to be excised in my comment as well as my phone call to the clinician. I can't speak much for the radiology where I work because I get wishy-washy reports most of the time... although this was called a SC LN by one radiologist and when it was sampled it was called "SC mass". I considered doing IHC, but I have such a scant amount of tissue... and since they are going to proceed with removing the 'mass', perhaps I should take a look at those H&Es first. At that point, it should be obvious (I hope).

I bottom-lined my dx as: "Benign-appearing thyroid epithelium without atypia (see comment)". My comment was not lengthy, but I covered the bases pretty well with everyone's comments above.

The funny thing is that my partner had a similar case two weeks ago that was labeled as "thyroid nodule" and contained nothing but thyroid tissue. There were no cyto-architectural features that would even suggest PTC. What made the story kind of funny was that the history only contained an ICD9 code that we googled as "non-toxic multinodular goiter". A few days later, the ENT called my partner and said that the biopsy came from an enlarged lymph node and, "Btw, the patient was recently diagnosed with PTC by FNA." He was confused as to why he received a categorically benign diagnosis. An addendum was made and my partner called malignant. A couple of days later after the call I received a frozen section on two lymph nodes as well as on the thyroid (metastatic PTC in the nodes, and pretty clear cut PTC on the thyroid). I guess this would one of the cases where metastatic PTC in a LN has deceptively bland histology.

 

[randomlogik]

I had a recent thyroidectomy case for PTC and one of the lymph nodes had a very cytologically bland looking foci of thyroid tissue. The cytology looked much different from the primary tumor. Everything I read on the topic is that these are treated as mets despite the bland histology. Your case is definitely challenging though if can't know for sure you are in a lymph node. With the clinically history, it needs to come out.

 

[schrute]

The funny thing is that my partner had a similar case two weeks ago that was labeled as "thyroid nodule" and contained nothing but thyroid tissue. There were no cyto-architectural features that would even suggest PTC. What made the story kind of funny was that the history only contained an ICD9 code that we googled as "non-toxic multinodular goiter". A few days later, the ENT called my partner and said that the biopsy came from an enlarged lymph node and, "Btw, the patient was recently diagnosed with PTC by FNA." He was confused as to why he received a categorically benign diagnosis. An addendum was made and my partner called malignant. A couple of days later after the call I received a frozen section on two lymph nodes as well as on the thyroid (metastatic PTC in the nodes, and pretty clear cut PTC on the thyroid). I guess this would one of the cases where metastatic PTC in a LN has deceptively bland histology.

Sounds typical..."Oh by the way the patient has a history of 'X,Y or Z' "...thanks, would have been nice to know that from the outset.

 

[Gene_]

There are IHC profiles that can help with this. http://ajcp.ascpjournals.org/content/126/5/700.full.pdf

I'd be interested to hear if anyone has ever had any luck with these stains. I've seen it attempted many times, but it was never helpful in resolving the diagnostic dilemma.

 

[deleted314957]

I expressed the need for this mass to be excised in my comment as well as my phone call to the clinician. I can't speak much for the radiology where I work because I get wishy-washy reports most of the time... although this was called a SC LN by one radiologist and when it was sampled it was called "SC mass". I considered doing IHC, but I have such a scant amount of tissue... and since they are going to proceed with removing the 'mass', perhaps I should take a look at those H&Es first. At that point, it should be obvious (I hope).

I bottom-lined my dx as: "Benign-appearing thyroid epithelium without atypia (see comment)". My comment was not lengthy, but I covered the bases pretty well with everyone's comments above.

The funny thing is that my partner had a similar case two weeks ago that was labeled as "thyroid nodule" and contained nothing but thyroid tissue. There were no cyto-architectural features that would even suggest PTC. What made the story kind of funny was that the history only contained an ICD9 code that we googled as "non-toxic multinodular goiter". A few days later, the ENT called my partner and said that the biopsy came from an enlarged lymph node and, "Btw, the patient was recently diagnosed with PTC by FNA." He was confused as to why he received a categorically benign diagnosis. An addendum was made and my partner called malignant. A couple of days later after the call I received a frozen section on two lymph nodes as well as on the thyroid (metastatic PTC in the nodes, and pretty clear cut PTC on the thyroid). I guess this would one of the cases where metastatic PTC in a LN has deceptively bland histology.

I hope you included a comment to the effect of -"I can't make chicken soup out of chicken ****".