Hypercalcaemia and cancer

Irish Stones

Once a vet told me that if a blood test reveals a hypercalcaemia, then it's advisable to investigate for the possible presence of a cancer, because hypercalcaemia is one of the symptoms of a cancer, though it doesn't mean that the cancer is sure, because it's a symptom of many other things as well.
But does the presence of a cancer always give hypercalcaemia in a blood test?
I mean, if a blood test has a normal value of calcium level in the blood, is this a clue that there's no cancer at all?
Thanks!

anniehoo

Irish Stones wrote: »

But does the presence of a cancer always give hypercalcaemia in a blood test?

There are many causes of hypercalcemia (it's really complicated to explain tbh) but no, while elevated calcium is one of the differentials for cancer, it's only raised in ~25% of cases and only certain types of cancer too.While it can be indicative of malignancy, it usually has to be established for awhile for hypercalcemia to occur so early stages of malignancy don't always show it.

This is worth reading especially the bit about Humoral hypercalcemia of malignancy

Irish Stones

Thanks, Anniehoo, interesting article!
I have read it, especially in the section that you pointed out.

Last year one of my two cats was found with a slightly over range calcium level, so my vet told me that among other causes the cancer should have been kept into consideration. Luckily a further test four months later showed normal values. So either it was an error from the lab or the cat was having a momentary problem that disappeared some weeks later.

My other cat has been diagnosed with a cancer, a carcinoma, but though she's been sick for the past two and a half years, her blood tests are perfect under every aspect, not even one value outside the ranges, including the calcium. She also suffers from CKD since she was 5, now she's 14.

My hope is that the doctors told me it was a cancer but they were wrong, this could explain why the cancer hasn't moved or changed in the past 30 months and why her blood tests are alright. But it's just a hope...

anniehoo

With blood testing, especially a biochemistry panel many factors can affect the results i.e. whether the animal has been fasted or not, has exercised or been stressed prior to sampling; whether the sample was placed in the correct tube; was it analysed that day or was it sent to an external lab etc If your cat's hypercalcemia was a one off and you don't know whether he'd eaten or not, then it should have been repeated. Fasting is best.

If "cancer" was suspected, calcium measurement on it's own is not diagnostic enough and should be interpreted in conjunction with a full biochemistry panel, including haematology. Parathyroid hormone also. If Lymphoma was suspected then the cat would possibly be anaemic (low PCV and Hgb) and have a high lymphocyte count, with a large amount of lymphoblasts on blood smear (microscopic) evaluation. A lymph node fine need aspirate can done to look for the presence of T and B cell lymphocytes also.

After all that, in cats (not so much dogs) there is a term "Idiopathic Feline Hypercalcemia IHC" which sounds fancy but basically means calcium is raised and they have no idea why , idiopathic just means "cause is unknown".

So, as you can see by isolating a single parameter of one blood test and trying to figure out a cause from just that one result is impossible and not recommended. Only after a full workup is done can a definite diagnosis (or not in the case of IHC) be made