Soft tissue sarcoma in Dogs (Canis) | Vetlexicon
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Soft tissue sarcoma

ISSN 2398-2942


Introduction

  • Soft tissue sarcoma are tumors arising from mesenchymal connective tissues. They are usually grouped together as they generally behave in a similar manner. The benign mesenchymal tumors, eg fibroma, are quite rare, locally expansile tumors that are cured by local surgical excision. These tumors by definition do not metastasize and they generally only cause clinical problems by their size or location. The malignant counterparts are generally referred to as ‘soft tissue sarcomas’ (STS) as they mostly present, behave, and are treated, in a similar manner.
  • STS account for 15-20% of all canine tumors: although incidence can vary according to breed - see below.
  • Signs: firm, fibrous mass affecting skin/subcutis, may be adherent to underlying tissue, slow growing.
  • Include:
  • Diagnosis: biopsy and histopathology.
  • Treatment: surgical resection +/- radiotherapy.
  • Prognosis: based on histological grade, mitotic index and evaluation of margins.

Presenting signs

  • Soft tissue sarcomas are usually bulky, fleshy tumors, as opposed to ulcerative masses as seen with carcinomas.
  • Soft tissue sarcomas may arise from any anatomic site. They most commonly present as a soft tissue mass of the skin or subcutis but can arise in deeper soft tissues or associated with body cavities and internal organs, they may also arise in oral and nasal cavities.
  • The tumor itself is usually painless. Pain or discomfort may occur when the tumor involves or abuts sensitive structures. A classic example of this is the neurofibrosarcoma of the brachial plexus as seen in the dog which presents with a progressive forelimb lameness and marked muscle wastage. Subcutaneous sarcoma of the limb can occasionally present as a very painful mass. This happens when the tumor grows underneath the fascial plane causing compartment syndrome and nerve compression. 
  • Tumors often appear well circumscribed or even encapsulated. In reality these tumors have poorly defined histological margins and often infiltrate along fascial planes. "Pseudencapsulation" is a feature of many sarcomas, the apparent capsule is infiltrated by tumor tissue.
  • Usually quite slow growing, although occasionally can show rapid progression, especially in young animals

Age predisposition

  • Generally occur in older animals (8-9 years old is typical), although younger animals of large breeds (eg Golden retrievers) may be affected.

Breed/Species predisposition

Pathogenesis

Etiology

  • Largely unknown in dog.
  • Occasionally associated with chronic inflammation.
  • Rarely arise at sites of burns or implants.
  • Rarely radiation induced.

Classification

  • According to presumed tissue of origin based on histological appearance of neoplastic cells and stroma:
    • Fibrosarcoma - fibrous connective tissue (when evidence of collagen formation is lacking, often referred to as ‘spindle cell sarcoma’).
    • Peripheral nerve sheath tumor (PNST) Nerve sheath: neoplasia.
    • Liposarcoma - adipose tissue.
    • Leiomyosarcoma - smooth muscle Leiomyoma  /Leiomyosarcoma.
    • Rhabdomyosarcoma - skeletal muscle.
    • Myxosaroma - myxoid stroma.
    • (Hemangiopericytoma Hemangiopericytoma - most now reclassified as PNST).
  • Some poorly differentiated tumors which lack cellular / stromal features to indicate tissue of origin may be referred to as ‘poorly differentiated’ or ‘anaplastic’ sarcoma.
  • The following may also be described as soft tissue sarcoma, but are ‘excluded’ from the following general description / management because their biological behavior is more aggressive:

Timecourse

  • Relatively slow growing.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Giancarlo A, Roberta R, Chambers J K, Miller A D et al (2021) Review of Histological Grading Systems in Veterinary Medicine.Vet Pathol online ahead of print PubMed DOI: 10.1177/0300985821999831.
  • Linden D, Liptak J M, Vinayak A et al (2019) Outcomes and prognostic variables associated with primary abdominal visceral soft tissue sarcomas in dogs: A Veterinary Society of Surgical Oncology retrospective study.Vet Comp Oncol 17,  265-270 PubMed DOI: 10.1111/vco.12456.
  • Bray J P (2017) Soft tissue sarcoma in the dog - part 2: surgical margins, controversies and a comparative review.  JSAP 58 (2), 63-72 PubMed.
  • Bray J P (2016) Soft tissue sarcoma in the dog - part 1: a current review.  JSAP 57 (10), 510-519 PubMed.
  • Demetriou J L, Brearley M J, Constantino-Casas F et al (2012) Intentional marginal excision of canine limb sarcomas followed by radiotherapy. JSAP 53 (3), 174-181 PubMed.
  • Dennis M M, McSporran K D, Bacon N J et al (2011) Prognostic factors for cutaneous and subcutaneous soft tissue sarcomas in dogs. Vet Pathol 48 (1), 73-84 PubMed.