Canis ISSN: 2398-2942

Bone cysts

Synonym(s): Aneurysmal bone cysts; Simple/unicameral bone cysts; Odontogenic/Radicular bone cysts

Contributor(s): Prof Mark Rochat, Chris Shales

Introduction

  • Signs: swelling (distal limb or mandible), pain (although most are pain free) and lameness.
  • Treatment: curretage and bone graft.
  • Diagnosis: radiography; histopathology.
  • Prognosis: good for odontogenic cysts and resection of cystic lesions; less certain for anuerysmal cysts.

Pathogenesis

Etiology

  • In dogs, bone cysts reportedly develop in the metaphyseal or diaphyseal regions of the distal portion of the radius, ulna, femur, tibia, or humerus (Schrader and others 1983).
  • Benign/Simple/Unicameral cysts: the proposed mechanism of cyst development involves local trauma, hematoma formation, osteoclast hyperplasia, and venous obstruction caused by local remodeling of bone, which causes accumulation of fluid (Resnick and others 1995).
  • Aneurysmal bone cysts: possibly secondary to an insult to the bone that disrupts bone marrow vasculature leading to arteriovenous shunting. Bony reaction and blood accumulation results in an expansile blood-filled cyst with cortical destruction resulting from increased local blood supply. A thin shell of bone is deposited by the periosteum as it is displaced (Barnhart 2002). There are reports of aneurysmal cysts associated with underlying pre-existing neoplasia in the dog and of a chondrosarcoma that occurred following surgical manipulation of a cyst (Barnhart 2002).
  • Odontogenic cysts Non neoplastic oral masses : rare in animals, and classification of the lesions tends to vary between authors. Odontogenic cysts are derived from cell rests of Malassez, cell rests of dental laminae, reduced enamel epithelium, or malformed enamel organs. Types of odontogenic cysts reported in dogs include radicular cysts, dentigerous cysts, and keratocysts. Radicular cysts Oral masses: radicular cyst contain an inflammatory infiltrate and can be associated with devitalized teeth. Dentigerous cysts are defined as cysts that contain part or all of a tooth, which is often malformed and often remains impacted or unerrupted (Doran and others 2008).

Predisposing factors

General
  • Trauma to the metaphyseal regions of bones of young animals.
  • Devitalized or malformed teeth.

Pathophysiology

  • Cysts can cause expansion of the bone and result in localized enlargement of the region (eg distal radius or mandible).
  • Lameness can be due to the expansile nature of the disease (periosteal discomfort, soft tissue compression) or secondary to pathological fracture either of the cyst wall or the bone itself.
  • Infection of cysts is a theoretical possibility.
  • Hemorrhage from aneurysmal bone cysts can be brisk.
  • Neoplastic transformation following surgical manipulation of a cyst has been suggested (Barnhart 2002).

Timecourse

  • The potential for pain free growth makes it impossible to define how rapidly these lesions develop or progress.

Epidemiology

  • Long bone cysts are reported to occur typically in dogs <18 months old (Schrader and others 1983) however there are reports of bone cysts affecting older animals (Duval and others 1995).
  • Aneurysmal and mandibular and maxillary odontogenic cysts have been reported in mature dogs.

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.
  • Doran I, Pearson G, Barr F & Hotson-Moore A (2008) Extensive bilateral odontogenic cysts in the mandible of a dog. Vet Pathol 45, 58-60 PubMed.
  • MacInnes T J, Thompson M S & Lewis D D (2005) Whats your diagnosis? JAVMA 227, 1561-1562 PubMed.
  • Sarierler M, Cullu E, Yurekli Y et al (2004) Bone cement treatment for aneurysmal bone cyst in a dog. J Vet Med Sci 66,1137-1142 PubMed.
  • Beckman B W (2003) Radicular cyst of the premaxilla in a dog. J Vet Dent 20, 213-217 PubMed.
  • Barnhart M D (2002) Malignant transformation of an aneurysmal bone cyst in a dog. Vet Surg 31 (6), 519-524 PubMed.
  • Stickle R, Flo G, Render J (1999) Radiographic diagnosis - benign bone cyst. Vet Rad and Ultrasound 40, 365-366 PubMed.
  • Nomura K, Sato K (1997) Pelvic aneurysmal bone cyst in a dog. J Vet Med Sci 59,1027-1030 PubMed.
  • French S L, Anthony J M G (1996) Surgical removal of a radicular odontogenic cyst in a four year old Dalmatian dog. J Vet Dent 13 (4), 149-151 PubMed.
  • Duval J M, Chambers J N & Newell S M (1995) Surgical treatment of an aneurysmal bone cyst in a dog. Vet Comp Ortho Traumatol 8 (4), 213-217 PubMed.
  • Poulet F M, Valentine B A, Summers B A (1992) A survey of epithelial odontogenic tumours and cysts in dogs and cats. Vet Pathol 29 (5), 369-380 PubMed.
  • Schrader S C, Burk R L, Lin S (1983) Bone cysts in two dogs and a review of similar cystic bone lesions in the dog. JAVMA 182 (5), 490-495 PubMed.

Other sources of information

  • Kelly Cet al(2001)The Use of a Surgical Grade Calcium Sulfate as a Bone Graft Substitute: Results of a Multicenter Trial.SECTION I SYMPOSIUM Clinical Orthopaedics & Related Research382, 42-50, January 2001.
  • Resnick D, Kyriakos M, Guerdon Det al(1995)Tumors and tumorlike lesions of bone: imaging and pathology of specific lesions.In: Resnick D, ed.Diagnosis of bone and joint disorders. 3rd ed. Philadelphia: WB Saunders Co. pp 35593576.
  • Halliwell W H (1993)Tumourlike lesions of bone.In:Disease mechanisms in Small Animal SurgeryBojrab MJ. Ed Philadelphia: Lea and Febiger. pp 932-943.


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