Epulis

Epulis (plural: epulides) is a generic term used in veterinary medicine to describe a benign, often slow-growing, mass or tumor-like lesion arising from the periodontal ligament or gingival soft tissues. The term is derived from the Greek word 'epoulis,' meaning 'a gumboil' or 'a growth on the gum.' In veterinary pathology, epulides are the most common benign oral tumors in dogs, and they are classified into three main histological types: fibromatous epulis, ossifying epulis, and acanthomatous epulis (also known as peripheral odontogenic fibroma, peripheral ossifying fibroma, and acanthomatous ameloblastoma, respectively). These lesions are typically firm, smooth or lobulated, and may be pedunculated or sessile. They arise from the periodontal ligament, which is the connective tissue that anchors the tooth to the alveolar bone. Epulides are generally non-metastatic but can be locally invasive, particularly the acanthomatous type, which may cause significant bone destruction. They are most commonly diagnosed in middle-aged to older dogs, with certain breeds showing a predisposition. In cats, epulides are less common but can occur, often with a more aggressive clinical course. The clinical significance of epulides lies in their potential to interfere with mastication, cause oral discomfort, and, in the case of acanthomatous epulis, lead to substantial local tissue destruction. Accurate diagnosis and appropriate surgical management are essential to prevent recurrence and preserve oral function.

The exact etiology of epulides remains unknown, but several factors have been implicated. Chronic inflammation of the gingival tissues, possibly due to periodontal disease, dental calculus, or chronic trauma, is considered a potential trigger for the proliferation of periodontal ligament cells. Genetic predisposition is evident in certain breeds, such as Boxers, Golden Retrievers, and Cocker Spaniels, suggesting a hereditary component. Hormonal influences have been proposed, as some epulides have been observed to grow during periods of hormonal change, although this is not well-documented. Viral etiologies have been investigated, but no specific viral agent has been consistently identified. The role of growth factors, such as transforming growth factor-beta (TGF-β) and bone morphogenetic proteins (BMPs), in the pathogenesis of ossifying epulis has been suggested, as these factors are involved in bone formation and may contribute to the osseous metaplasia seen in this type. Acanthomatous epulis is thought to arise from the rests of Malassez, which are epithelial remnants of the Hertwig's epithelial root sheath, and its locally invasive behavior is attributed to the proliferative capacity of these cells. Overall, the etiology is likely multifactorial, involving a combination of genetic susceptibility, local inflammatory stimuli, and possibly hormonal or growth factor influences.

Epulides are the most common benign oral tumors in dogs, accounting for approximately 30-40% of all canine oral tumors. They are less common in cats, where they represent a smaller percentage of oral masses. In dogs, the median age at presentation is around 8 years, with a range of 1 to 15 years. There is no strong sex predilection, although some studies suggest a slight male predominance. Breed predispositions include Boxers, Golden Retrievers, Cocker Spaniels, Beagles, and Shetland Sheepdogs. Brachycephalic breeds may be at higher risk due to dental crowding and increased periodontal disease. In cats, epulides are rare, but when they occur, they may be more aggressive, with a higher recurrence rate. The incidence of epulides is not influenced by geographic location or seasonality. The condition is typically sporadic, with no known environmental risk factors beyond those associated with periodontal disease. The prevalence of each histological type varies: fibromatous epulis is the most common, followed by ossifying epulis, while acanthomatous epulis is less frequent but more clinically significant due to its invasive nature.

The pathophysiology of epulides involves the proliferation of cells derived from the periodontal ligament. In fibromatous epulis, there is a dense proliferation of fibrous connective tissue, with variable amounts of collagen and fibroblasts. The lesion is typically covered by stratified squamous epithelium, which may be hyperplastic. Ossifying epulis is characterized by the presence of bone or osteoid within the fibrous stroma, indicating metaplastic bone formation. This is thought to occur due to the differentiation of pluripotent mesenchymal cells into osteoblasts, possibly stimulated by local growth factors. Acanthomatous epulis arises from the epithelial rests of Malassez, which are remnants of the Hertwig's epithelial root sheath. These cells proliferate and form islands or cords of epithelial cells within a fibrous stroma. The acanthomatous type is locally invasive, with the ability to infiltrate underlying bone, causing osteolysis. This invasiveness is mediated by the production of matrix metalloproteinases (MMPs) and other enzymes that degrade the extracellular matrix. Despite its aggressive local behavior, acanthomatous epulis does not metastasize to regional lymph nodes or distant organs. The growth of epulides is typically slow, and they may remain asymptomatic for long periods. However, as they enlarge, they can cause mechanical interference with mastication, tooth displacement, and secondary ulceration and infection.

Several factors predispose to the development of epulides. Chronic periodontal disease is a significant risk factor, as the associated inflammation may stimulate the proliferation of periodontal ligament cells. Poor oral hygiene, dental calculus accumulation, and gingivitis are common in affected animals. Breed predisposition suggests a genetic component, with certain breeds having a higher incidence. Age is a factor, as epulides are more common in middle-aged to older animals. Trauma to the gingiva, such as from chewing on hard objects or dental procedures, may also contribute. Immunosuppression, whether due to disease or medication, may increase susceptibility to oral masses. In cats, retroviral infections (FIV, FeLV) may predispose to oral tumors, although the association with epulides is not well-established. Hormonal influences have been suggested, but evidence is limited. Additionally, the presence of other oral lesions, such as gingival hyperplasia, may increase the risk. Overall, the interplay of genetic, inflammatory, and environmental factors likely contributes to the development of epulides.

Clinical signs of epulides depend on the size, location, and type of the lesion. Small epulides may be asymptomatic and discovered incidentally during routine oral examination. As the lesion grows, common signs include a visible mass on the gingiva, which may be smooth, lobulated, or ulcerated. The mass may be pedunculated or sessile and can vary in color from pink to red. Dogs may exhibit halitosis, excessive drooling, difficulty prehending or chewing food, and weight loss. They may paw at the mouth or show signs of oral pain, such as reluctance to eat hard food or vocalization when eating. In cases of acanthomatous epulis, bone invasion can lead to tooth mobility, loosening, or loss. The lesion may bleed easily, especially if traumatized. In advanced cases, facial swelling or deformity may be evident. Cats with epulides may show similar signs, but they may be more subtle, such as decreased appetite or grooming changes. Systemic signs are uncommon unless secondary infection or significant oral discomfort leads to decreased food intake and weight loss.

The differential diagnoses for epulides include other oral masses and tumors. Key differentials include: 1) Peripheral odontogenic fibroma (which is essentially the same as fibromatous epulis, but the term is used interchangeably); 2) Gingival hyperplasia, which is a non-neoplastic proliferation of gingival tissue, often drug-induced (e.g., cyclosporine, amlodipine) or due to chronic inflammation; 3) Oral papillomatosis, caused by papillomavirus, which presents as multiple cauliflower-like lesions, typically in young dogs; 4) Squamous cell carcinoma, a malignant tumor that is locally invasive and may metastasize, often presenting as an ulcerated, proliferative mass; 5) Fibrosarcoma, a malignant mesenchymal tumor that is locally aggressive and may metastasize; 6) Malignant melanoma, a highly malignant tumor with a high metastatic rate, often pigmented; 7) Osteosarcoma of the jaw, which is a malignant bone tumor that may present as a firm swelling; 8) Ameloblastoma, a benign but locally invasive epithelial tumor of odontogenic origin; 9) Eosinophilic granuloma complex in cats, which can present as oral ulcers or masses; 10) Foreign body granuloma, due to a retained foreign body such as a grass awn. Definitive diagnosis requires histopathology, as clinical appearance alone is not sufficient to differentiate these conditions.

The diagnostic approach to a suspected epulis begins with a thorough oral examination under general anesthesia, including inspection and palpation of the mass, assessment of tooth mobility, and evaluation of regional lymph nodes. Dental radiographs are essential to evaluate the extent of the lesion, particularly for bone involvement. Radiographic findings may include soft tissue swelling, bone lysis, or periosteal reaction. For a definitive diagnosis, a biopsy is required. An incisional biopsy is preferred for larger masses to obtain a representative sample, while an excisional biopsy may be performed for small lesions. The biopsy should be submitted for histopathological evaluation. Advanced imaging, such as computed tomography (CT), may be indicated for large or invasive lesions, especially acanthomatous epulis, to assess the extent of bone destruction and plan surgical excision. CT is particularly useful for evaluating the maxilla and mandible. In cases where malignancy is suspected, thoracic radiographs and lymph node aspiration may be performed to rule out metastasis. The diagnostic algorithm should also include a complete blood count, serum biochemistry, and urinalysis to assess overall health and anesthetic risk. The final diagnosis is based on histopathology, which will classify the epulis type and guide treatment.

Laboratory findings in animals with epulides are typically unremarkable, as the condition is localized and does not cause systemic metabolic disturbances. A complete blood count (CBC) may be normal, although mild leukocytosis may be present if there is secondary infection or inflammation. Serum biochemistry profile is usually within normal limits. In cases of significant oral pain or difficulty eating, there may be mild dehydration or electrolyte imbalances, but these are non-specific. Urinalysis is generally normal. If the animal is a candidate for surgery, a coagulation profile may be recommended, especially if there is a history of bleeding disorders. In cats, testing for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) may be considered, as these infections can affect the immune system and surgical outcomes. However, there are no specific laboratory biomarkers for epulides. The diagnosis relies on histopathology, which is the gold standard.

Imaging plays a crucial role in the evaluation of epulides. Dental radiography is the primary imaging modality and is essential for assessing the extent of the lesion, particularly for detecting bone involvement. Radiographic findings may include a soft tissue opacity mass, bone lysis, or periosteal reaction. In cases of acanthomatous epulis, bone lysis is often prominent, and the lesion may appear as a radiolucent area with irregular borders. Dental radiographs are also useful for evaluating tooth roots and periodontal structures. For larger or more invasive lesions, computed tomography (CT) is recommended. CT provides detailed three-dimensional information about the extent of the mass, bone destruction, and involvement of adjacent structures such as the nasal cavity or orbit. CT is particularly valuable for surgical planning, as it allows for accurate assessment of tumor margins. Magnetic resonance imaging (MRI) is less commonly used but may be indicated for soft tissue extension or for evaluating the extent of the lesion in the oral cavity. Thoracic radiographs are recommended if malignancy is suspected, to rule out pulmonary metastasis, although epulides are benign and do not metastasize. Ultrasonography is not typically used for oral masses, but it may be used to evaluate regional lymph nodes for metastasis.

Cytology may be performed via fine-needle aspiration (FNA) of the mass, but it is often non-diagnostic for epulides due to the dense fibrous nature of the lesion. FNA may yield a few spindle cells or epithelial cells, but it cannot reliably differentiate between the types of epulis or rule out malignancy. Therefore, histopathology is the gold standard for diagnosis. An incisional biopsy is recommended for large masses, while an excisional biopsy may be performed for small lesions. Histologically, fibromatous epulis is characterized by a proliferation of dense fibrous connective tissue with variable collagen deposition, covered by hyperplastic stratified squamous epithelium. The stroma may contain fibroblasts, collagen fibers, and occasional inflammatory cells. Ossifying epulis shows similar features but with the presence of bone or osteoid within the stroma. The bone may be mature or immature, and there may be evidence of osteoblastic activity. Acanthomatous epulis is characterized by islands or cords of epithelial cells within a fibrous stroma. The epithelial cells may show acanthomatous change, with intercellular bridges and a tendency to form keratin pearls. The lesion is not encapsulated and may infiltrate the surrounding bone. Special stains, such as Masson's trichrome for collagen or von Kossa for calcium, may be used to highlight specific features. Immunohistochemistry may be used to differentiate epulides from other tumors, but it is not routinely necessary.

The treatment of choice for epulides is surgical excision. The extent of surgery depends on the type and size of the lesion. For fibromatous and ossifying epulides, a conservative excision, such as a marginal resection, may be sufficient. The mass is removed with a margin of normal tissue, and the underlying bone is curetted if necessary. For acanthomatous epulis, a more aggressive approach is required due to its invasive nature. A wide surgical excision, including the affected tooth and surrounding bone, is recommended. This may involve a mandibulectomy or maxillectomy for large lesions. In cases where complete excision is not possible, radiation therapy may be considered. Radiation therapy has been shown to be effective in controlling acanthomatous epulis, with a high success rate. However, it is associated with potential side effects, such as osteonecrosis and the development of secondary tumors. Cryotherapy has also been used, but it is less effective than surgery or radiation. Medical therapy with nonsteroidal anti-inflammatory drugs (NSAIDs) may be used to manage pain and inflammation, but it does not treat the underlying lesion. Postoperative care includes pain management, antibiotics if there is evidence of infection, and a soft diet for a period of time. Regular dental check-ups are essential to monitor for recurrence.

The prognosis for epulides is generally excellent, especially for fibromatous and ossifying types, which are benign and have a low recurrence rate after complete excision. The recurrence rate for these types is reported to be less than 10%. Acanthomatous epulis has a higher recurrence rate, ranging from 20% to 50%, if not completely excised. However, with wide surgical excision or radiation therapy, the prognosis is good, with a long-term control rate of over 90%. The prognosis is worse if the lesion is incompletely excised or if there is significant bone involvement. Negative prognostic factors include large tumor size, invasion into bone, and incomplete surgical margins. The overall survival time for animals with epulides is not significantly different from that of healthy animals, as the condition is benign and does not metastasize. However, the quality of life may be affected if the lesion interferes with eating or causes pain. With appropriate treatment, most animals have a good to excellent prognosis.

Post-treatment follow-up is essential to monitor for recurrence and ensure proper healing. After surgical excision, the animal should be re-examined at 2 weeks to assess wound healing and remove sutures if necessary. A dental examination should be performed at 3, 6, and 12 months postoperatively, and then annually thereafter. During these examinations, the oral cavity should be inspected for any signs of recurrence, and dental radiographs may be taken if there is concern. For acanthomatous epulis, more frequent monitoring may be recommended, such as every 3 to 6 months for the first year. If radiation therapy is used, follow-up should include assessment for radiation-induced complications, such as mucositis, osteonecrosis, or the development of secondary tumors. The owner should be educated on the importance of good oral hygiene, including regular brushing and professional dental cleanings, to reduce the risk of periodontal disease and potential recurrence. Any changes in eating habits, drooling, or the appearance of a new mass should be reported immediately.

Pearls: 1) Always perform a thorough oral examination under anesthesia in any dog with a suspected oral mass, as small epulides may be missed in an awake patient. 2) Dental radiographs are essential to assess bone involvement, especially for acanthomatous epulis, which can cause significant bone lysis. 3) A biopsy is mandatory for definitive diagnosis; do not rely on clinical appearance alone. 4) For acanthomatous epulis, consider CT imaging for surgical planning, as it provides better assessment of tumor extent than dental radiographs. 5) Radiation therapy is an excellent alternative for acanthomatous epulis when surgery is not feasible or for incompletely excised lesions. Pitfalls: 1) Do not mistake an epulis for a malignant tumor and perform an overly aggressive surgery without a biopsy. 2) Avoid incomplete excision, especially for acanthomatous epulis, as this leads to a high recurrence rate. 3) Do not neglect to evaluate regional lymph nodes, even though epulides are benign, to rule out other conditions. 4) Be cautious with the use of NSAIDs in animals with renal or hepatic disease, as they can cause adverse effects. 5) Do not forget to consider drug-induced gingival hyperplasia as a differential, especially in animals on cyclosporine or amlodipine.

There are no specific drug protocols for the treatment of epulides, as the primary treatment is surgical. However, perioperative medications are commonly used. Antibiotics may be indicated if there is evidence of secondary infection or as prophylaxis during surgery. A common choice is amoxicillin-clavulanate (Clavamox) at a dose of 12.5-25 mg/kg PO q12h for 7-10 days. Alternatively, clindamycin (Antirobe) at 5.5-11 mg/kg PO q12h for 7-10 days is effective against oral anaerobes. Pain management is crucial postoperatively. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as carprofen (Rimadyl) at 2.2 mg/kg PO q12h or meloxicam (Metacam) at 0.1 mg/kg PO q24h (after a loading dose of 0.2 mg/kg) can be used for 3-5 days. Opioids such as tramadol at 2-5 mg/kg PO q8-12h may be used for more severe pain. If radiation therapy is employed, supportive care may include oral rinses with chlorhexidine (0.12%) to prevent infection, and sucralfate (Carafate) at 0.5-1 g PO q8h to manage mucositis. In cases of acanthomatous epulis where surgery is not possible, radiation therapy is the treatment of choice, and no specific drug protocol is used. It is important to adjust dosages in animals with renal or hepatic impairment and to monitor for adverse effects.

The veterinary literature on epulides is relatively limited, but several studies provide evidence for the classification and treatment of these lesions. A landmark study by Gardner (1991) classified epulides into three types and described their histopathological features. Subsequent studies have confirmed the benign nature of fibromatous and ossifying epulides and the locally invasive behavior of acanthomatous epulis. A study by Verstraete et al. (1992) reported on the surgical management of oral tumors in dogs, including epulides, and found that complete excision resulted in a low recurrence rate. Another study by Thrall (1981) demonstrated the efficacy of radiation therapy for acanthomatous epulis, with a control rate of over 90%. More recent studies have focused on the use of CT for surgical planning and the role of immunohistochemistry in differentiating epulides from other tumors. The ACVIM consensus statement on the diagnosis and treatment of oral tumors in dogs and cats (2016) provides guidelines for the management of epulides, emphasizing the importance of histopathology and appropriate surgical margins. Overall, the evidence supports surgical excision as the treatment of choice, with radiation therapy as an effective alternative for acanthomatous epulis.