Page 48 - VetCPD Jnl Volume 7, Issue 4

VETcpd - Surgery
Peer Reviewed
Soft Tissue Sarcomas in Dogs
Soft tissue sarcomas are common in dogs. Surgical therapy is the mainstay of treatment, and wide margins of 3cm laterally and a deep fascial plane are recommended where anatomically possible. As some reports suggest that local recurrence may be less common in low-grade tumours of the distal limb, marginal excision can be employed in areas where wide resection cannot be achieved. Radiation therapy and/or metronomic chemotherapy can be used as adjunctive therapy where there has been marginal excision and/or dirty histopathological margins.
Alison Moores BVSc(Hons) CertSAS DipECVS FRCVS
Alison graduated from the University of Bristol in 1996. She spent four years in general practice, and worked at the Royal Veterinary College for seven years as an Intern, Resident and then Lecturer in Small Animal Surgery. She joined Anderson Moores Veterinary Specialists in 2008 where she works as a Soft Tissue Surgeon. Alison became a Diplomate of the European College of Veterinary Surgeons in 2005, and is an RCVS Recognised Specialist in Small Animal Surgery and
a Fellow of the RCVS.
Alison regularly gives lectures and webinars to vets and nurses, both in the UK and abroad. She is the Surgery Program co-ordinator for the BSAVA certificate program and an examiner for the RVC’s CertAVP. She has been an external examiner for the certificate program at Edinburgh University.
She is involved with the veterinary community and has volunteered as Associate Editor of the Journal of Small Animal Practice, been a member of the BSAVA Education committee and spent 10 years on the committee of the Association of Veterinary Soft Tissue Surgeons, most recently as President.
She co-edited the second edition of the BSAVA 'Manual of Canine and Feline Wound Management and Reconstruction’ and has published many book chapters and clinical and research papers
E: alison.moores@andersonmoores.com
Key words: soft tissue sarcoma, dog
Introduction
Soft tissue sarcomas are common in dogs, representing 4% of all skin tumours and 20% of the malignant skin tumours.
‘Soft tissue sarcoma’ is the name given
to a group of mesenchymal tumours with similar biological features that are indistinguishable from each other on light microscopy.This group of tumours includes: fibrosarcoma, liposarcoma, malignant fibrous histiocytoma, mesenchymoma, myxosarcoma, non- plexus derived peripheral nerve sheath tumours, perivascular wall tumours
and undifferentiated sarcoma. Other sarcomas that are easily distinguishable from each other on light microscopy, and have different biological behaviour, are not considered as part of the ‘soft tissue sarcoma’ group, and include: haemangiosarcoma, synovial cell sarcoma and brachial- or lumbosacral- plexus derived peripheral nerve sheath tumours.
They are pseudoencapsulated masses with ill-defined margins.The pseudocapsule
is fibrous tissue formed from the compression and atrophy of normal tissue around the tumour. It has traditionally been thought that the pseudocapsule contains active tumour cells and that tumour cells can cross the pseudocapsule.
Presentation
Soft tissue sarcomas occur most commonly in middle-aged or elderly, medium or large breed dogs, with no breed predisposition.Tumours are most likely to develop on the limbs (60%)
or trunk (35%).Typically there is no predisposing cause, although tumours can arise from previous sites of inflammation, e.g. fracture sites.Tumours may be small or large on presentation, and while some tumours do seem to grow rapidly, most
have been slow growing for weeks to months prior to presentation.Tumour size may not be an important risk factor for outcome, rather it is adherence to deep structures that predicts recurrence and death from tumour related disease. Other presenting complaints, such as lameness or ulceration, are uncommon.
Diagnostic Evaluation
It is important to know what a skin
mass is before commencing treatment. Unfortunately, there is still a tendency
for veterinary surgeons to remove a
mass without knowing if it is a tumour
or what tumour type it is.This can lead
to performing an inappropriately small surgery, particularly for intermediate- or high-grade tumours, which may lead
to recurrence, or may require dogs to undergo additional surgery or radiation therapy to achieve clean margins. Similarly, dogs with benign or low-grade tumours may undergo excessively large resections.
Differential diagnoses for a cutaneous
or subcutaneous mass include, but
are not limited to: inflammatory or infectious (e.g. granuloma, abscess), cyst, haematoma, benign tumour (e.g. cornifying epithelioma, haemangioma, histiocytoma, trichoepithelioma, lipoma) and malignant tumour (e.g. soft tissue sarcoma, high-grade mast cell tumour, malignant melanoma).
A diagnosis can be easily made using cytology to rule out the readily exfoliating tumours, such as lipoma and mast cell tumour. Furthermore, there is good-to-excellent diagnostic accuracy of soft tissue sarcomas submitted to specialists for interpretation (Ghisleni et al. 2006). However, false negative results are disproportionately high in cytology samples examined ‘in-house’, either due
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