All's not swell

About six weeks ago Katie, my GSD, developed a large swelling on her rump. As you can see from the picture, it is about saucer size. I took her to our vet who guessed that it might be a strain and prescribed anti-inflammatory tablets. Since then there has been no change whatsoever. I took her back this evening and a different vet stated that she had never come across such a swelling high up on the rump. The swelling is very hard and not pliable at all. It does not cause any discomfort to Katie and she is fit and active in every way. She runs, performs, eats and even sleeps on that side without any reaction.
The vet gave us two options - one, leave well alone and see what happens, or two, carry out an investigation with a biopsy. I am reluctant to take option two as I am sure the other dogs have experienced similar swellings and I would be most grateful if you could offer some suggestions.
Brian Gore, Bath

This is the type of conundrum they might give vet students at college! Let’s break it down into possible causes and see what we can do to make progress in this case.
We have a firm, circular, soft tissue swelling on the right rump of diameter about 15cms across and about five centimetres high. The mass is forward of the hip on the right side of the spine in the area approximately over the sacro-iliac joint. It is apparently painless and was unresponsive to anti-inflammatories.
A simplified list of the different diagnoses would look like this:

Trama
• Bone fracture
• Haematoma
• Bruising

Infection
• Parasites – worms under the skin
• Bacteria – abscess
• Yeast – less likely
• Fungi – dermatomycosis

Neoplasia (Cancer)

Auto-immune disease
• eg dermatomyositis

Allergy
• Environment
• Food

Congenital/Hereditary Disease

I hope this list gives you an inkling of what goes through every vet’s mind during every consultation. We all chat and smile and look after your animal, but actually we’ve got a list something like this in our heads and we’re actually ticking things off even as you enter the consulting room.
On this list we can initially remove fractures as we haven’t got any pain. Parasites are a possibility and could be easily investigated, as with infection. Allergy is less likely as there are no other signs (itching or hair loss). The same is true for inherited diseases, but auto-immune disease would only be investigated using full biopsy of the mass.
My feeling in this situation would be to consider a Fine Needle Aspirate Biopsy (FNAB) initially. This is where the vet, usually without having to sedate the patient, inserts a fine needle into the lump then draws back on an attached syringe. If there is no pus or blood to serum in the lump, initial diagnosis is immediately possible. The material removed from the lump can be sent for analysis to identify it microscopically.
Ultrasound scanning of the lump is another simple tool that could allow the vet to gain, simply, information on the mass without being too invasive.
I would suggest doing the above needle biopsy and ultrasonography and then making a decision from there as to where to go in treatment or further tests.
All medicine, be it conventional or complementary, is best performed where a full diagnosis has been made.
If the vets diagnose it as a harmless benign lump of some sort, you can rest easy.
Nick Thompson, holistic vet