Investigating Oral Masses

Vet Times The website for the veterinary profession https://www.vettimes.co.uk

INVESTIGATING ORAL MASSES

Author : Vicki Rubasinska

Categories : Vets

Date : May 31, 2010

VICKI RUBASINSKA underlines the importance of identifying oral cancers, details treatment options and provides an overview of the likely long-term prognosis

ORAL tumours are not uncommon in dogs and cats.

They may be benign or very malignant – and, unfortunately, their gross appearance is not a good guide to their behaviour. It is important that all oral tumours are appropriately investigated.

A pet may be presented for obvious oral discomfort, bleeding, halitosis or eating difficulties. Growths are often large by this time, and if a lesion is aggressive, treatment may be more complicated.

Early detection is necessary to ensure better outcomes. It is vital that every animal has its mouth fully examined when presented to the surgery. This can help to identify early lesions that owners may not have noticed.

Benign growths in dogs include gingival hyperplasia and fibromatous and ossifying epulides. These are restricted to the gingiva. An acanthomatous epulis (or acanthomatous ameloblastoma) is classified as benign, but usually invades bone and requires more aggressive treatment1. In cats, eosinophilia granulomas are the most common benign growth. Suspected eosinophilic ulcers also need to be investigated to ensure they are not actually an erosive tumour2.

The most common tumours in dogs are squamous cell carcinoma (SCC), fibrosarcoma and melanoma3. SCC and fibrosarcoma are the most common types presented in cats3.

1 / 7 Other tumours affecting the oral cavity include adenocarcinomas of the salivary glands, undifferentiated carcinomas, osteosarcomas, lymphoma, mast cell tumours, giant cell tumours, neurofibromas and myxofibrosarcomas4. See Table 1 for a list of differential diagnoses.

Epulides

Epulides are very common in dogs, and are classified into fibromatous, ossifying and acanthomatous types.

They arise from the periodontal connective tissue and do not metastasise. However, acanthomatous epulides are very invasive into the surrounding bone, and require either radical surgery or radiotherapy to deal with them effectively. Radiotherapy was thought to be associated with inducing new tumours to develop at a later date, but this has not been confirmed with further reviews1.

Even with the fibromatous and ossifying lesions, it is important to excise the periodontal tissues involved to prevent recurrence – teeth can be displaced by these masses as well. Radiography is vital for any oral mass – even if it just looks like an epulis – to see if there is bone involvement.

Eosinophilic granuloma complex (EGC)

Nodular granulomas can be found on the hard palate, palatine arches and tongue.

Eosinophilic ulcers commonly occur on the upper lips and hard palate. The classic presentation is of bilateral ulcers on the upper lips adjacent to the philtrum. These lesions form part of a complex that also includes skin lesions, and is a hypersensitivity reaction – usually to fleas or mosquitoes. However, the external appearance is not pathogonomic and biopsies should be taken for confirmation2.

This ulceration can occur over branches of the palatine artery, resulting in a persistent haemorrhage due to trauma by the tongue. As the blood will be swallowed, it is often not apparent to the owner until symptoms of anaemia are present. The lesion can be hard to identify due to the very pale mucosa, but it is usually adjacent to the canine5.

Most EGC lesions will respond to corticosteroids, as well as the removal of the inciting cause, such as effective flea control. A bleeding ulcer may require a mattress suture, and treatment for the anaemia.

Common neoplastic lesions

SCC

2 / 7 – Gingiva. SCC is a rapidly growing, invasive neoplasm. It is the most common oral malignancy in cats; the second most common in dogs. Gingival SCC is highly invasive into bone. The appearance can be raised, irregular, necrotic and/or ulcerative. The risk of metastasis is species dependent; it is rare in cats, spreading more commonly to lymph nodes than to lungs. However, in dogs, metastasis also depends on the site – rostral oral lesions rarely spread, but caudal oral masses have a higher metastatic rate.

– Lingual. SCC arising on the tongue is rarer, but occurs more frequently in cats than dogs. The lesion in cats is usually on the ventrolateral surface of the body of the tongue at the level of the reflection of the frenulum. In dogs, they occur more commonly on the dorsal tongue. The mass grows rapidly and is highly metastatic to regional lymph nodes and lungs (approximately 40 per cent).

– Tonsillar. SCC can arise from the tonsillar fossa epithelium and invades the tonsillar lymphoid tissue. These tumours are invasive, but also spread very quickly to lymph nodes (98 per cent), lungs (63 per cent) and other organs (20 per cent).

Melanoma

This is the most common oral malignancy in dogs, and the third most common in cats. It has a high metastatic rate in dogs (80 per cent), though this tends to be local lymph nodes, rather than the lungs. Melanomas arise from the gingival surface and vary in appearance – including raised, non- encapsulated, irregular, ulcerated and necrotic – and may not be pigmented. They are highly invasive to bone.

Fibrosarcoma

This is the second most common oral malignancy in the cat, and the third most common in the dog. It grows slowly, but still creates invasive tumours. Metastasis is uncommon.

Diagnostic work up

A basic investigation should include biopsy of the mass and radiography of the affected area to ascertain if there is bone involvement and how extensive this is. To provide an indication of the type of lesion, radiography is a very useful tool in the early stages of investigation. Radiographing the area of interest before taking the biopsy is highly recommended, so you have more of an idea of what you are cutting into. You will be able to provide the client with more information about the likely nature of the mass as well.

to 1f). Figures 2a to 2c. These OralRadiographs masses canfor the look SCC, very osteosarcoma similar, but may and be ameloblastoma of very different are origins shown (see in Figures 1a images illustrate the amount of bone loss that can occur.

3 / 7 Depending on where the mass is, a simple parallel radiography technique may be sufficient to see the extent of the bone involvement. However, it is often necessary, and easier to interpret, if intra- oral plates and a bisecting-angle technique are used to acquire the images. Good imaging is important if aggressive surgery or radiotherapy is considered1.

More advanced imaging modalities, such as CT or MRI, also have a role in some cases. Maxillary SCC has been shown to affect the orbit in some cats6. However, the same paper did not show any correlation between the extent of mass extension and lymph node involvement with the survival time. MRI is regarded as more accurate in assessing oral tumour margins in soft tissue and bone than CT7.

Biopsies need to be deep enough to acquire a diagnostic sample. The clinical picture can be complicated by secondary gingivitis and osteomyelitis, and the underlying disease may be missed.

If there is obvious bone involvement, or any other reason for concern about the mass being aggressive, fineneedle aspirates of the regional lymph nodes would be indicated. However, only 17 per cent of palpably enlarged submandibular lymph nodes were positive for metastatic disease (cytology correlated well with histopathology), and only examining these lymph nodes is likely to underestimate the incidence of metastasis3. It is worthwhile to consider thoracic radiographs, and whether – or when – to take them. In the same study, 7.4 per cent of cases had radiographic evidence of metastatic disease.

The World Health Organisation (WHO) has a staging system for oral tumours, which is simply an anatomical system for describing the extent of the primary tumour, lymphnode in volvement and presence of metastasis. The human version is frequently revised, given the complexity of the anatomical area and the various types of tumours that arise there8. For animals, the basic tumour, to 6 Tables 2 ).node and metastasis (TNM) system is useful for assessing the extent of the disease (see

When applied to acanthomatous epulides, this staging system has been shown to be useful to indicate prognosis, as dogs with WHO stagethree tumours have a 7.9 times higher risk of recurrence than dogs with stage-one tumours.

Treatment options

The main treatment options are surgery and radiotherapy. The position and extent of local infiltration affect the possible success of surgery. As laboured already, good imaging is paramount in planning surgery and radiotherapy to achieve the best result first time.

The different tumour types require different surgical margins, depending on how infiltrative they are. Well-differentiated melanomas on mucous membranes in dogs may be treated with local excision only9. It is recommended that an acanthomatous epulis has 2cm margins past gross or

4 / 7 radiographically visible disease1. It is often necessary to consider full, partial or hemimandibulectomies or maxillectomies to achieve sufficient margins. These surgeries can be associated with significant morbidity, although dogs may cope better than cats. Postoperative care should include feeding tube placement until the animal is able to eat again10.

Radiotherapy is often used as an adjunctive treatment to surgery, for palliation of inoperable tumours or, in the case of acanthomatous epulides, as the sole treatment. The different tumours vary in their sensitivity to radiation (see Table 6).

Side effects of radiation include mucositis in the treated region of the oral cavity. Skin effects in the treatment field include hair loss, erythema and scaling. Later, variation in pigmentation of the skin – either loss of or increased – will also occur. Radiation over the laryngeal area can result in fibrosis and constrictions in this area1.

Treatment may also include immunogene therapy. In dogs, vaccination with a non-canine tyrosinase gene can stimulate the immune system to attack melanoma cells and increase survival time11.

Photodynamic therapy uses a photosensitive compound that is accumulated in the neoplastic tissue. On activation with visible light, the compound causes reactive oxygen species to be released, resulting in cellular damage and death. It is used quite extensively in human medicine, and has been trialled in dogs12.

Piroxicam and, potentially, other cyclo-oxygenase-2 inhibitors may also have a role in the treatment of some oral cancers. In dogs, it has been used in the management of oral SCC, sometimes in combination with other chemotherapy agents, such as cisplatin13.

Despite a less frequent expression of COX-2 receptors on feline SCC, NSAIDs have been shown to increase survival. This may be due to analgesia and non-specific reduction in inflammation associated with the mass, rather than a direct antineoplastic effect14.

Prognosis and follow up

Adequate excision (or drug treatment) of benign lesions should be curative. Regular follow-up appointments should be made to check for recurrence.

Survival rates vary, depending on the tumour and the treatment given. Few animals will survive more than six months with lingual or tonsillar SCC, regardless of treatment. Dogs with fibrosarcoma and gingival SCC treated with excision alone have a median survival of seven to 11 months. Longer survival rates have been reported with melanoma in dogs, where complete excision has been possible. However, in cats with melanoma, the prognosis is very poor – less than 60 days.

5 / 7 An accurate prediction of survival is always difficult, especially as it may influence the lengths to which the owner will go for treatment. A thorough initial investigation – to obtain the most information regarding the type of tumour, degree of local invasion and spread to lymph nodes or distant sites – means the severity of disease can be accurately presented to the owner. The most appropriate treatments can then be discussed, and hopefully a plan can be agreed that will ensure the best outcome for the patient with regard to quality of life and longevity4.

• To download published Veterinary Times articles, log on to www.vetsonline.com

References and further reading

1. Mayer M N and Anthony J M (2007). Radiation therapy for oral tumors: canine acanthomatous ameloblastoma, CVJ 48: 99-111. 2. Foster A (2003). Clinical approach to eosinophilic granuloma complex, In Practice 25: 2-9. 3. Herring E S, Smith M M and Robertson J L (2002). Lymph node staging of oral and maxillofacial neoplasms in 31 dogs and cats, J Vet Dent 19(3): 122-126. 4. Tilley L M and Smith Jr F W K (2004). Five-Minute Veterinary Consult Canine and Feline (3rd edn), Lippincott Williams and Wilkins, Philadelphia: 31, 58, 422, 481, 824-825, 936-937, 1,222, 1,228, 1,229. 5. Malik R (2003). Diseases of the ears, nose, throat and oral cavity of cats, Proceedings of the WSAVA World Congress. 6. Gendler A, Lewis J R, Reetz J A and Schwarz T (2010). Computed tomographic features of oral squamous cell carcinoma in cats: 18 cases (2002-2008), J Am Vet Med Assoc 236(3): 319-325. 7. Bertone E R, Snyder L A and Moore A S (2003). Environmental and lifestyle risk factors for oral squamous cell carcinoma in domestic cats, J Vet Intern Med 17(4): 557-562. 8. Patel S G and Shah J P (2005). TNM staging of cancers of the head and neck: striving for uniformity among diversity, CA Cancer J Clin 55: 242-258. 9. Esplin D G (2008). Survival of dogs following surgical excision of histologically well- differentiated melanocytic neoplasms of the mucous membranes of the lips and oral cavity, Vet Pathol 45(6): 889-896. 10. Northrup N C, Selting K A, Rassnick K M, Kristal O, O’Brien M G, Dank G, Dhaliwal R S, Jagannatha S, Cornell K K and Gieger T L (2006). Outcomes of cats with oral tumors treated with mandibulectomy: 42 cases, J Am Anim Hosp Assoc 42(5): 350-360. 11. McKnight P J J, Novosad A, Charney S, Farrelly J, Craft D, Wulderk M, Jeffers Y, Sadelain M, Hohenhaus A E, Segal N, Gregor P, Engelhorn M, Riviere I, Houghton A N and Wolchok J D (2003). Long-term survival of dogs with advanced malignant melanoma after DNA vaccination with xenogeneic human tyrosinase: a phase-one trial, Clin Cancer Res 9 (4): 1,284-1,290. 12. Osaki T, Takagi S, Hoshino Y, Okumura M, Kadosawa T and Fujinaga T (2009). Efficacy of antivascular photodynamic therapy using benzoporphyrin derivative monoacid

6 / 7 ring A (BPD-MA) in 14 dogs with oral and nasal tumors, J Vet Med Sci 71(2): 125-132. 13. Boonsoda S and Wanikiat P (2008). Possible role of cyclooxygenase– two inhibitors as anticanceragents, The Veterinary Record 162: 159-161. 14. Hayes A M, Adams V J, Scase T J and Murphy S (2007). Survival of 54 cats with oral squamous cell carcinoma in UK general practice, J Small Anim Pract 48(7): 394-399. 15. Blackwood L and Dobson J (1998). Radiotherapy in small animal oncology, In Practice 20: 566-575.

7 / 7