Parathyroid nodule?

Re: Parathyroid nodule?

Martin Atkinson — Fri, 01 Aug 2014 14:11:43 GMT

I did a partial thyroidectomy at the same time, I left a small bit of visually normal thyroid tissue attached to the caudal blood supply, other than that I excised the capsule, all the visibly abnormal tissue with associated thyroid plus a bit more within the constraints of such a narrow surgical field.

Histo says: DESCRIPTION: Attached to the thyroid gland capsule is a discrete mass lesion arising from parathyroid tissue that features a cluster of solid nodules and an adjacent larger cystic structure with a discontinuous wall of similar glandular tissue. The nodules and cyst feature a uniform population of small cuboidal to polyhedral cells that form closely packed cords and occasional microfollicular structures, supported by a thin fibrovascular stroma. Along the cyst wall the cells pile up to several layers deep in some areas, with few micropapillary projections, whereas other regions have a flattened/attenuated single layer. Individual cells have a modest amount of finely granular lightly eosinophilic cytoplasm and ovoid darkly stippled nuclei with small to inapparent nucleoli. There are scattered mitotic figures, occasionally up to 4 mitoses/400x field, and with rare atypia. The cyst wall is surrounded by an encapsulating band of fibrous tissue that contains patchy perivascular lymphoid aggregates. In areas where the cyst wall is degenerate, there are aggregates of cholesterol clefts, macrophages and focal fibroplasia, with multiple small mineralised bodies. The adjacent thyroid gland appears partially compressed, with a focal nest of parathyroid tissue that appears to be infiltrating/pushing into the edge of the thyroid parenchyma. There is a separate small hyperplastic nodule of thyroid tissue.

MORPHOLOGICAL DIAGNOSIS: PARATHYROID GLAND CARCINOMA. PROGNOSIS: Fair to guarded

COMMENT: The histological features are consistent with a parathyroid gland tumour, which is probably of low-grade malignancy. The tumour is partially cystic, with few smaller solid nodules. Parathyroid carcinoma is a rare tumour in domestic animals. Adenomas are usually functional, causing signs of hyperparathyroidism, principally skeletal demineralization and hypercalcaemia, but carcinomas are often non-functional. Carcinomas tend to be larger tumours and frequently invade through the capsule into adjacent structures (thyroid gland, cervical muscles). Carcinomas may metastasize to local lymph nodes and to the lung. In the sections examined, there is suggestion of early infiltration into the thyroid gland, but the outer edges of the tumour appear well-demarcated. The surgical margins in sections are minimal (< 0.5 mm), so ongoing monitoring is warranted. Note that the adjacent thyroid gland also contained a solitary hyperplastic nodule*.

* NB I assume this means hyperplastic thyroid tissue

Spoken to Gerry Polton and he says no need for further action/chemo.

Re: Parathyroid nodule?

Andrew Kent — Fri, 01 Aug 2014 12:39:06 GMT

Sound good so far! Did you remove the thyroid on that side as well (i.e. do you think you have got it all)?

Andy

Re: Parathyroid nodule?

Martin Atkinson — Wed, 30 Jul 2014 11:29:04 GMT

[quote user="Martin Atkinson"] I removed the lump and it looked just like a thyroid cyst, some normal thyroid tissue but nothing that looked like a parathyroid.[/quote]Further update:

Not like me to have self-doubt but decisions vindicated. Histology revealed a parathyroid carcinoma infiltrating into the thyroid capsule but other margins clear. So far calcium remains in low normal range. Will keep testing calcium daily until the end of the week. Keep you posted if it goes tits up but we've done all the right things so far.

Re: Parathyroid nodule?

Martin Atkinson — Mon, 28 Jul 2014 13:00:07 GMT

Update:

Cat came in this morning to excise the mass. It had been on Vit D analogue for 24 hrs, its total Ca this morning was 2.17 mmol/l (first time its been normal!) phos was 1.21. I removed the lump and it looked just like a thyroid cyst, some normal thyroid tissue but nothing that looked like a parathyroid. Oh well its now had a left sided thyroid/parathyroidectomy its off to the lab we'll wait and see.

Best laid plans of mice and men and all that!

Re: Parathyroid nodule?

Andrew Kent — Tue, 22 Jul 2014 17:41:07 GMT

Hi Martin,

Looking at the most recent case we had we used 1 drop twice daily to start and it was a pretty small cat so i'm sure you would be fine with that.

Interestingly that cat did go hypocalcaemic after surgery (we hadn't pre-treated)

Andy

Re: Parathyroid nodule?

Martin Atkinson — Tue, 22 Jul 2014 16:20:19 GMT

Rory and Andrew: I have got the Alpha-One alfacalcidol drops (only used AT 10 drops before). Working on your suggested dose Andrew of 10 ngm/kg bid the cat will require 45 ngm bid. Given the stuff contains 100 ngm/drop this may prove difficult. However, as BSAVA formulary states that the dose for hyopcalcaemia is 10-15 ngm/kg bid (45 - 67.5 ngm bid) then I presume this shouldn't present much of a problem!

Re: Parathyroid nodule?

Rory Bell — Mon, 21 Jul 2014 16:33:39 GMT

Hi Martin

That's exactly right. Duration of suppression is variable, but at least in part dependent on pre-op calcium (and possibly PTH) concentrations. The critical period for hypocalcemia is in that gap between dissipation of PTH produced from the autonomously functioning gland pre-op and the remaining glands re-booting and regaining function post op. In dogs, clinical tetany is most commonly seen 4-7 days post op. No one knows if the same time frames are applicable to cats; I don't think that clinical tetany has been described in a cat post parathyroidectomy (not because it does not exist, but more likely because it's a rare disease in cats).

cheers!

Re: Parathyroid nodule?

Martin Atkinson — Mon, 21 Jul 2014 15:20:34 GMT

Thanks for that. I presume the problem with possible hypocalcaemia is that the contra-lateral parathyroid gland has been suppressed by the over-active one and takes a little while to get going again?

Re: Parathyroid nodule?

Rory Bell — Mon, 21 Jul 2014 15:18:12 GMT

AS Andy said, much better to have contemporaneous total calcium rather than a day old ionised calcium result. Aim to have total calcium in the low end of the normal range, especially as phosphate may increase slightly and you want the Ca x Po4 product below 6 to avoid any nephrocalcinosis given that this cat is already azotaemic.

cheers

Re: Parathyroid nodule?

Andrew Kent — Mon, 21 Jul 2014 14:25:12 GMT

Ah, I see. So we would start the alfacalcidol the night before surgery and continue afterwards whilst monitoring calcium. If it goes low then increase the alfacalcidol dose (sometimes you need massive doses) but remember each dose increase can take a few days to have effect. If calcium remains stable for a few weeks then gradually taper down the dose of alfacalcidol over a few weeks whilst monitoring calcium.

Andy

Re: Parathyroid nodule?

Martin Atkinson — Mon, 21 Jul 2014 13:04:46 GMT

[quote user="Andrew Kent"]Alfacalcidol is interchangeable with calcitriol, has similar speed of onset etc and is easier to dose due to oral suspension so we use alfacalcidol in all of these cases and don't keep anything else[/quote] Not sure if I posted the question clearly enough, but do you pre-med with the Vit D only or post op as well and if the latter how long? I know the answer to that question when I have a hypo-calcaemic patient due to iatrogenic parathyoid damage post bi-lateral thyroidectomy but this will be first parathyroidectomy.

Re: Parathyroid nodule?

Andrew Kent — Mon, 21 Jul 2014 11:55:29 GMT

[quote user="Martin Atkinson"]Questions: does it need more than alphacalcidol post -op i.e.calcitriol (or should I just have some ready in case it goes hypocalcaemic) and given the added difficulty and cost of testing ionised Ca is serum calcium level Ok for monitoring?[/quote]

Alfacalcidol is interchangeable with calcitriol, has similar speed of onset etc and is easier to dose due to oral suspension so we use alfacalcidol in all of these cases and don't keep anything else. You can assume a similar dose range between the two.

I have in previous jobs used total calcium to monitor these cases without any problems and think it is more important to be able to get the result quickly rather than being a day behind by submitting an iCa externally so would use the total calcium unless there are any problems.

I would also make sure you have an IV calcium preparation in case of severe clinical hypocalcaemia but think it is fairly unlikely you will need it.

Andy

Re: Parathyroid nodule?

Martin Atkinson — Mon, 21 Jul 2014 11:42:45 GMT

[quote user="Rory Bell"]Great case, let us know how you get on![/quote]OK so the cat is booked in for surgery. The owner doesn't want it to be hospitalised post op and TBH as there is no-one here overnight it is a little pointless so the compromise is she will bring it in daily for blood tests.

Questions: does it need more than alphacalcidol post -op i.e.calcitriol (or should I just have some ready in case it goes hypocalcaemic) and given the added difficulty and cost of testing ionised Ca is serum calcium level Ok for monitoring?

Re: Parathyroid nodule?

Robin Grimmer — Fri, 18 Jul 2014 21:59:42 GMT

Hi Martin, I had a memorable case of this that I used as a case for my cert SAM! Geri cat, wt loss, pu/pd, unilateral goitre. Bloods similar to yours. I did do PTH assay on mine which was high and proceeded with surgery. Histo confirmed a parathyroid adenoma. The cat did will initially, Ca returned to normal, I had no problems with hypocalcaemia. However, the cat died 6 months later of renal failure due to the nephrotoxic effects of the previous prolonged hypercalcaemia. I'd be inclined to get the cat in pronto, iv fluids pre and post-op and whip it out. Keep the cat in for a few days and monitor Ca levels closely.

Re: Parathyroid nodule?

Rory Bell — Fri, 18 Jul 2014 21:23:05 GMT

Ah well, at least the rest of my post is (hopefully) useful. That will teach me to post on Vetsurgeon in a hurry! ;-)

Re: Parathyroid nodule?

Martin Atkinson — Fri, 18 Jul 2014 15:16:17 GMT

Thanks Andrew for your help on the case and putting Rory straight - it wasn't that well hidden!!

Re: Parathyroid nodule?

Andrew Kent — Fri, 18 Jul 2014 15:07:08 GMT

Hi Rory,

[quote user="Rory Bell"]If you wanted to differentiate between renal 2ndry and primary HPTH, then measuring ionised calcium might help, as ionised hypercalcemia would be anticipated with primary HPTH[/quote]

Martin did measure iCa at the start, its just hidden in the text of the original post:

[quote user="Martin Atkinson"]ionised ca 2.08 > 1.4 comment when adjusted to pH 7.4 is slightly higher[/quote]

T4 also:

[quote user="Martin Atkinson"]TT4 16.6 nmol/l normal[/quote]

Glad you agree otherwise :-)

Andy

Re: Parathyroid nodule?

Andrew Kent — Fri, 18 Jul 2014 15:04:20 GMT

[quote user="Hannah Wynne Richards"]

Funny how something which a practitioner would call a dreadful case becomes a great one to an academic!

Wynne

[/quote]

It's nothing to do with being an academic (not that I would call myself an academic) but surely everybody likes seeing the cases that are a bit out of the ordinary day to day stuff?!

Re: Parathyroid nodule?

Rory Bell — Fri, 18 Jul 2014 14:44:00 GMT

Hi Martin

Sorry to have come late to this discussion. Did you measure T4 in this cat? Something to bear in mind is that as this cat is azotaemic, renal secondary hyperparathyroidism is a possibility. Over 80% of cats with CRF have increased PTH concentrations. If you wanted to differentiate between renal 2ndry and primary HPTH, then measuring ionised calcium might help, as ionised hypercalcemia would be anticipated with primary HPTH, but very uncommon in CRF, unless its end stage renal failure.

That said, from what little we know about HPTH in cats, this cat would appear to have read a textbook. They frequently are azotaemic (very uncommon in dogs with HPTH) and commonly are hypophosphatemic which your cat appears to be. This also makes renal 2ndry HPTH less likely as almost all of these cats will be hyperphosphatemic. Cats with primary HPTH often have nodules which, in a dog with HPTH, would be deemed massive, so being able to palpate a PTH mass is actually not that unusual in a cat with HPTH. One word of caution - PTH carcinoma (rather than adenoma) appears to be much more common in cats with HPTH than it is in dogs. I don't know if this nodule appears freely movable or not, but local invasion would be a possibility here and might make surgery more tricky. Other than that, completely agree with what Andy has said.

Great case, let us know how you get on!

Re: Parathyroid nodule?

Martin Atkinson — Fri, 18 Jul 2014 12:32:22 GMT

[quote user="Hannah Wynne Richards"]

Funny how something which a practitioner would call a dreadful case becomes a great one to an academic!

Wynne

[/quote]No I think its a great case, I'm definitely the glass half full type and really juicy abscess is a great abscess not a bad one.

Re: Parathyroid nodule?

Hannah Wynne Richards — Fri, 18 Jul 2014 12:19:00 GMT

Funny how something which a practitioner would call a dreadful case becomes a great one to an academic!

Wynne

Re: Parathyroid nodule?

Andrew Kent — Fri, 18 Jul 2014 12:07:25 GMT

Sounds a great case.

We would use alfacalcidol (One-Alpha oral drops) and start the night before surgery at around 10ng/kg BID. We then tend to keep them hospitalised for at least 3-5 days afterwards and monitor their calcium daily. If all stays normal we will taper down the alfacalcidol over a month or so.

Do let us know how it goes!

Andy

Re: Parathyroid nodule?

Martin Atkinson — Fri, 18 Jul 2014 11:15:22 GMT

[quote user="Andrew Kent"]Why not look at whether this is a functional mass with PTH/PTHrp before excision,[/quote]We have now tested PTH (84pg/ml ref <40) and PTHrP (<0.1pmol/l >1 suggestive of malignancy). The nodule is unilateral and feels round and pea sized rather than the oval bean shape that thyroid nodules normally take. I now assume this is a primary benign parathyroid nodule and intend excising I see no value in ultrasound as we would have to refer for that anyway. In my long career this is the first one I've diagnosed and been in a position to treat so no experience. Anything else you would suggest other than the Vit D supplement and how long would you suggest treating prior to surgery?

Re: Parathyroid nodule?

Laura Marshall — Wed, 02 Jul 2014 18:14:37 GMT

I had a feline case, similar to this, who had a functional parathyroid cyst. Unilateral ventral cervical swelling and hypercalcaemic, FNA of goitre just revealed fluid +++. Hypercalcaemia panel to Dechra lab showed PTH very elevated. Unfortunately owners did not want to go down the road of surgery, and that cat was PTS as became dyspnoeic.

Re: Parathyroid nodule?

Andrew Kent — Wed, 02 Jul 2014 18:05:00 GMT

Why not look at whether this is a functional mass with PTH/PTHrp before excision, as this could be an idiopathic hypercalcaemic with an incidental nodule. I would want to know this first because if this is a functional parathyroid nodule I would pre-treat with vitamin D before surgical excision with that ionised calcium as there would be a high chance of post-op hypocalcaemia.

Ultrasound of the region would also help you to see the origin of the mass and is not that technically difficult.

Andy