Possible sarcoma dog tarsus

Zak is an 8 year old Golden Retriever, who is healthy, full of life, but has developed a small lump on the right tarsus (see attached photo). The lump was first noticed some 3 weeks ago and a fine needle aspirate has been performed by our local vests (report is detailed blow). He has for the last 2 weeks been on reduced activity, just to rule out exercise as an issue. When walking he shows no signs of a limp or any pain.

When mobilised the lump does feel as if it is connected to the bone structure (rather than just the skin) and appears to be soft to the touch.

The vets report to the layperson is inconclusive and could suggest simple fluid around the joint or a soft tissue sarcoma!

From what I have read, if this is a sarcoma, then the aspirate should have been conclusive and we should have received a grading, 1, 2, 3. The vet had 2 attempts to aspirate the lump, the first withdraw was very limited and clear fluid, the second looked just like blood. Might this inconclusive Cytology report be the result of a poorly performed aspirate?

Does anyone have any experience of this with their dog and what our next steps should be (repeat the aspirate, conduct a core biopsy, x-ray, CT, etc?

REPORT
Cytology report:
Six submitted smears of aspirates from a soft 2 cm diameter mass over the right tarsus ?sarcoma

DESCRIPTION
Nucleated cellularity is moderately low and cell preservation is moderate to good. There is a very pale eosinophilic fluid background containing very large numbers of erythrocytes, occasional clumps of platelets and numerous strands of fibrin which entrap a moderate proportion of the nucleated cells preventing evaluation. In areas the erythrocytes are seen windrowing (lining up in row). Nucleated cells are predominantly large mononuclear cells, often with abundant variably vacuolated cytoplasm (activated appearance), with lesser numbers of small lymphocytes. There are low numbers of non-degenerate neutrophils in numbers proportionate to the amount of background blood. In addition, there are occasional aggregates of atypical mesenchymal cells. Individual cells are generally caudate in appearance with wispy indistinct cell borders and a moderate amount of mid to dark basophilic cytoplasm. Nuclei are round to plump oval, ranging in size from 1x up to 3 times RBC diameter with coarse stippled chromatin and up to 7 small variably shaped prominent basophilic nucleoli

INTERPRETATION
Markedly haemodiluted viscous fluid with moderate mesenchymal proliferation (see comment)

COMMENT
The cytological appearance of the background fluid is reminiscent of synovial fluid. Given the location an outpouching of the joint capsule or synovial bursa is a consideration. Whilst small numbers of mesenchymal cells can be seen in synovial aspirates reflecting aspiration of synovial membrane the cells are typically quite bland. Here the mesenchymal cells are quite large and display moderate atypia. This is excessive for normal joint capsule. It may possibly reflect highly reactive synovium but I am concerned for a neoplastic mesenchymal population here (sarcoma). In particular, given the nature of the background, a synovial sarcoma.

Sorry this reply is not more helpful but the best thing you can do is speak to your vet - or if you are not confident in him; get a second opinion.

As much as we would like to help, we are primarily pet owners and our veterinary knowledge is limited. Even if someone has experienced something similar, every diagnosis is different.

I am truly sorry not to have anything better to offer and hope you get reassurance.

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agreed - I'd get a 2nd opinion, & soon. // Doing both a needle-aspiration AND a core biopsy might avoid the indeterminate conclusion - the pathologist might get a better look at the suspect cells.

I hope it's a minor rupture, but removing a sarcoma with decent margins & getting it early is also hopeful. Don't despair - there's hope, yet. Even if it's a sarcoma that's entered the bone, amputation with or w/o a prosthesis can mean a good chance of a normal lifespan, & amazingly, dogs do well on 3 legs; a rear limb is easier to cope with than a forelimb loss, especially in dogs over 40#.
He's 8, now, & if caught early B4 metastases, he could well live to 12 or even 14, barring other developments. [If he's kept lean, his chances of cancer are less than than they are if his BMI hits 30% or over.]

Holding good thoughts for U & Zak,
- terry

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soft-tissue sarcoma -
Soft Tissue Sarcoma in Dogs

Below is entirely a "just in case" resource, but if U don't need it, @zakky123 , someone searching for help with osteosarcoma or lung-metastases in the future, might -- so i put it here.

Signs of Osteosarcoma Lung Mets in Dogs, Cats and Treatment Options

Hope springs eternal,
- terry

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As has been said, have a chat with your vet/get a second opinion, and please do let us know what transpires.

Thank you for the replies.

I suppose the purpose of my post was to gain more of an insight into situation we find ourselves in at present. For my own medical condition, I use on a daily basis internet discussion forums, which has helped me over the last 17 years.

I am afraid that my vet does not give me a "warm fuzzy" feeling, but then again I do not totally trust my own doctors. Hence the use of forums to understand and validate my own doctors.

I am drawing a conclusion that the next step is a punch biopsy (had one myself for squamous cell carcinoma), this should give a more accurate diagnosis. As Zak has to be sedated for this, we may as well perform an X-ray with Contrast.

I will post the outcome, once the above tests have been performed.

Thank you again.

Thanks for the update. Best wishes for it all.