Faecal Occult Blood Test

Case of the Month (Mike James May 2010)

Canine and Feline Epulides

 Introduction

Epulis is a generic term for any tumour or tumour-like growth on the gingiva. In dogs and cats the term is most frequently applied to neoplastic growths that arise from the mesenchyme of periodontal ligament stroma or gingival epithelium. These occur frequently in dogs and rarely in cats and mainly arise from periodontal ligament (82%; Yoshida et al., 1999).

Epulides of periodontal ligament origin


These are mainly fibromatous epulides, but also include ossifying and giant cell variants. These are benign neoplasms that need to be distinguished from inflammatory granulation tissue or early malignant gingival tumours such as squamous cell carcinoma, fibrosarcoma and amelanotic melanoma. 

Gross findings:
  • Firm to hard, pale grey-pink growths.
  • Often project from between teeth or from the hard palate adjacent to the teeth.
  • Frequently mushroom shaped with a smooth lobulated surface.
  • Most common around carnassial and canine teeth of brachycephalic breeds and are mainly in dogs older that 3 years of age.
Histopathological findings:
  • Interwoven bundles of mature collagen form a major structural component of these growths (fig.1).
  • In this collagen stroma there may be extensive areas of osseous metaplasia (fig. 2) or multiple multinucleated giant cells.
  • The overlying mucosal surface is frequently hyperplastic and also may be ulcerated with accompanying inflammation.
  • The inflammatory cells remain superficial and do not penetrate the neoplastic tissue, unlike inflammatory granulation tissue that can have a somewhat similar gross appearance.
Biological behaviour and treatment:

These neoplasms are cured by complete excision. However, because they are attached to the periosteum and many are located between teeth, it may be difficult to get a clean deep margin. Incompletely excised tumours will recur and their continued growth will cause displacement of adjacent teeth. However, these epulides do not invade bone. Metastases have not been reported.

Acanthomatous ameloblastoma

These can be easily confused clinically with epulides of periodontal ligament origin as well as other gingival tumours and inflammatory nodules.
Gross findings:
  • Similar to fibromatous epulides.
Histopathological findings:
  • Composed of sheets, nodules and anastomosing cords of polyhedral epithelium bordered by a row of cuboidal to columnar cells.
  • Prominent intercellular bridges are a defining feature of these lesions (fig. 3).
Biological behaviour and treatment:
  • More locally invasive than fibromatous epulides.
  • Frequently invade underlying bone, but do not metastasise.
  • Complete surgical excision is curative, but wide margins may be necessary. A 2cm margin has been recommended (Mayer and Anthony, 2007).
  • Sensitive to radiation therapy and this may be an alternative treatment for those tumours that are not amenable to surgical excision. In the past there has been concern that this treatment may cause transformation to squamous cell carcinoma. However, a more recent retrospective study of 57 dogs  (McEntee et al., 2004) found no evidence to support this concern. The study concluded that radiation therapy is a safe and effective method of treatment for acanthomatous ameloblastomas.

Epulides in cats
  • Classified similarly to those of dogs.
  • In one study fibromatous, ossifying and giant cell epulides were 57.7%, 5.8% and 28.8% respectively (de Bruijn et al., 2007).
  • Acanthomatous epulides accounted for the remaining 7.7%.
  • Feline giant cell epulides represent a higher proportion of these growths compared to dogs, and also are much more locally aggressive than their canine counterpart.

Feline giant cell epulides

Gross findings:
  • Exophytic, polypoid and cherry red gingival growths.
Histopathological findings:
  • Composed of a complex of mesenchymal cells that have an immature fibrous-spindle cell appearance. Frequent prominent vascular and osseous areas. 
  • Moderate numbers of mitoses may be observed.
  • Giant cells are a prominent and defining feature (Fig 4.).
  • Giant cells resemble osteoclasts and are thought to arise from a monocyte/ macrophage-like precursor. Feline giant cell epulides will invade bone.
  • Metastases have not been reported.

Diagnostic Protocol
  • Epulides can not be diagnosed by cytology. FNAB may help with some malignancies (melanoma, squamous cell carcinoma, soft tissue sarcoma and round cell malignancies).
  • Histopathology is the appropriate diagnostic procedure. The entire growth, or as much as reasonably possible, should be submitted to ensure there is adequate tissue to rule out an underlying malignancy. Diagnosis by histopathology is often limited by inadequate sample size.

Pic1Pic2
Fig1. Fibromatous epulis in a dog showing interwoen bundles of mature collagen (long arrow) and hyperplastic gingival mucosa (short arrow)Fig 2. Ossifying epulis in dog showing multiple foci of osseous metaplasia (arrows).

Pic3pic4
Fig 3. Acanthomatous ameloblastoma in a dog showing intercellular bridging between polyhedral epithelial cells (arrow)Fig 4. Feline giant cell epulis showing osteoclast-like giant cells (arrow)

References

De Bruijn ND, Kirpensteijn J, Neyens IJS, Van den Brand JMA, van den Ingh TSG, 2007. A clinicopathological study of 52 feline epulides. Vet Pathol 44:161-9.
Mayer MN, Anthony JM, 2007. Radiation therapy for oral tumours: canine acanthomatous ameloblastoma. Can Vet J 48:99-101.
Thall DE, 1989.
McEntee MC, Page RL, Theon A, Erb HN, Thrall DE, 2004. Malignant tumour formation in dogs previously irradiated for acanthomatous epulis. Vet Radiol Ultrasound 45:357-361.
Yoshida K, Yanai T, Iwasaki T, Sakai H, Ohita J, Kati S, Minami T, Lackner A, Masegi T, 1999. Clinicopathological study of canine oral epulides. J Vet Med Sci  61:897-902.

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