Could you leave a MCT....?!

RE: Could you leave a MCT....?!

Kate Richardson — Mon, 09 Oct 2023 19:01:14 GMT

Or David Mills even

RE: Could you leave a MCT....?!

Kate Richardson — Sun, 08 Oct 2023 09:23:35 GMT

100% agree with David Milks

RE: Could you leave a MCT....?!

janine redman — Sat, 07 Oct 2023 12:48:52 GMT

I have seen malignant mast cell tumours in Nova Scotia duck tolling retrievers and labradors , in particular when they are around the prepuce and mammary or genital areas, however there are large numbers of older dogs with small solitary lesions which are mast cells on cytology but owners do not wish to operate . Especially where massive surgical intervention has been done previously. Most of these require no treatment or topical steroids and rarely cause a problem . I have had a number on the ears of golden retrievers where the disfigurement surgery would do meant owners were reluctant to operate and some of these remaine quiescent for the rest of the dog’s lives.

RE: Could you leave a MCT....?!

David Mills — Fri, 06 Oct 2023 14:42:01 GMT

I remember about a decade ago that MCTs were the big scary tumours and people were doing all sorts before removal - scanning the abdo, FNA'ing the spleen, x-raying the whole dog etc. before taking huge margins with considerable morbidity.

What quite motivated this may not be 100% clear but certainly it was a lack of knowledge about how these behaved and more recently there has been a thankful rowing back to something more sensible.

Most MCTs in my experience as a first opinion practitioner are benign and only some of these cause any kind of problem locally which may be settled by a course or repeated course of meds (preds, antihistamines). I cannot recall ever seeing one metastasise but then this is a skewed opinion as they are normally removed. But quite how long they would take to metastasise if left? Whether they would even metastasise? I've no idea.

This dog is old for its breed. I would be very cautious about doing anything whatsoever with a difficult mass to remove - the risks of causing far more problems than benefits are significantly high from what I can see. I suspect that this mass will not cause the dog any issues whatsoever, or shorten its life.

RE: Could you leave a MCT....?!

Rob Loxley — Fri, 06 Oct 2023 12:55:21 GMT

If it's a MCT and you leave it then it's unlikely to go away, may grow and cause more problems locally or distantly. I'd discuss whether they would ever want to remove it, if so then best dealt early while small and not ulcerated, metastasised etc. However we certainly have clients that elect not to, especially where it seems to be an endless stream of new tumors developing, and that's their option.
You could consider a TKI but I'd rather something likely to be curative (for this lump, though further de novo MCTs seem likely), or Stelfonta. I'm not aware of evidence for TKIs that they can prevent de novo MCTs in these cases?

RE: Could you leave a MCT....?!

Mayank Seth — Fri, 06 Oct 2023 09:35:16 GMT

Heavy initial caveat that I'm a medic, not an oncologist! with that said, here goes:

In theory one is supposed to treat each new MCT as a distinct entity and it is certianly reported that dogs with a history of low grade MCTs can then develop a high grade one, but my impression is that this is rare. I would be guided in part by whether there was any reason to suspect this new one is higher grade (size, speed of progression, systemic signs, cytologic grade etc) as to how worried to be. If some of these factors are of concern I would perhaps err more towards addressing the tumour early. If they are not then it becomes a bit more of a balanced judgement - its probably low grade and won't bother the dog, but it might! I would respect the decision of the owner to ignore it as long as they acknowledge there is a (small?) proportion of cases that have more significant tumours that are best addressed early.

Of course, as an alternative you could consider non-surgical treatment such as tigilanol tiglate but the pros and cons of considering using that on a dog's head are a whole different discussion and one well outside of my experience!