Tumours of the oral cavity

Question 1

Differential diagnoses for oral masses

Answer 1

NEOPLASIA

Gingival hyperplasia - boxer dogs!

Eosinophilic granuloma - cats

Craniomandibular osteopathy - WHWT

Question 2

What do suspect if oral mass in boxer dog?

Answer 2

Gingival hyperplasia

Question 3

What do suspect if oral mass in cats?

Answer 3

Eosinophilic granuloma

Question 4

What do suspect if oral mass in WHWT?

Answer 4

Craniomandibular osteopathy

Question 5

Epidemiology of oral tumours

Answer 5

The oral cavity is a common site for the development of tumours in small animals, superceded only by the skin and soft tissues, mammary tumours and haematopoeitic tumours.

Malignant oral tumours account for about 6 % of all canine cancers and 3 % of feline cancers.

Oral tumours generally arise in older animals.

Question 6

Pathology of oral tumours

Answer 6

A broad spectrum of tumour types.

Tumours range from the benign “epulides” to the more aggressive squamous cell carcinoma, fibrosarcoma and the highly malignant melanoma.

Malignant melanoma is more common in small, older dogs. Sarcomas more common in retriever type breeds.

SCC not that breed specific.

Question 7

Clinical signs of oral tumours

Answer 7

Dysphagia,

Halitosis,

Excessive salivation, purulent / blood stained saliva

Oral haemorrhage,

Displacement or loss of teeth

Facial swelling.

Question 8

Imaging techniques for oral tumours

Answer 8

Good quality radiographs of the tumour site are important to evaluate the extent.

Lateral and dorso-ventral/ ventro-dorsal views of the skull may be useful but dental, intra-oral films provide better detail.

Ultrasound is not generally very helpful for imaging tumours of the oral cavity but CT and MRI are being used increasingly for evaluation of such tumours for pre-surgical planning.

Question 9

Bony changes that can occur in association with oral tumours

Answer 9

osteolysis (may be punctate or permeative, or occasionally expansile bony lesions)

irregular periosteal new bone

mineralization of soft tissue tumours.

Question 10

Biopsy/FNA of oral tumours

Answer 10

Usually anaesthetise for biopsy and radiographs

Cytology is of limited value in the tumour but is important for evaluation of enlarged submandibular lymph nodes.

Most intra-oral neoplasms are accessible for biopsy. However, their surface may be infected or necrotic and hyperplastic or inflammatory reactions in the adjacent tissues are common thus care must be taken to ensure a representative sample.

Question 11

What type of biopsy should be used for oral tumours

Answer 11

As many oral tumours involve the underlying bone a deep wedge or Jamshidi needle-type biopsy is recommended.

Question 12

Staging of oral tumours

Answer 12

Primarily by physical examination and radiography.

More than half the tumours occurring at this site are malignant.

The lymphatic drainage of the oral cavity is primarily to the submandibular lymph nodes.

Regional drainage is to the retropharyngeal nodes and via the cervical chain to the prescapular and anterior mediastinal nodes.

The tonsils should also be evaluated especially in the case of malignant melanoma.

Question 13

Surgery for oral tumours

Answer 13

The most effective means of treatment.

The entire tumour must be excised with adequate margins of surrounding normal tissue.

Since a high proportion of oral tumours involve bone it is essential that the surgical margins are achieved in the bone as well as in the soft oral tissues.

Mandibulectomy and maxillectomy permit wide local excision of oral tumours with 1 - 2 cm margins of resection and have been used successfully in the management of basal cell carcinoma, squamous cell carcinoma and low grade fibrosarcoma.

Question 14

Radiotherapy for oral tumours

Answer 14

Offers the advantage of treating larger areas of tissue surrounding the tumour than may be possible by surgery and high energy megavoltage radiation has good penetration of bone.

Local lymph nodes can also be included in the treatment fields where necessary.

The main indication for radiotherapy is in the treatment of oral tumours which are not amenable to surgical excision.

Quite successful as a single agent in the management of gingival carcinomas in the dog and for palliation of oral malignant melanoma.

The combination of surgery with post-operative radiotherapy is probably the most effective treatment for oral sarcomas in the dog.

Radiotherapy has been less successful in the management of malignant oral tumours in the cat.

Question 15

Chemotherapy for oral tumours

Answer 15

Does not play a role in treatment of most oral tumours in the cat or in the dog with the exception of muco-cutaneous forms of lymphoma.

Question 16

Benign Tumours of the Oral Cavity

Answer 16

The “Epulides”

a group of common, non-metastatic oral tumours arising in association with the gingiva.

represent up to 40% of all oral tumours in the dog, they are relatively uncommon tumours in the cat.

Question 17

What are the two distinct tumour groups that make up the “Epulides”?

Answer 17

benign fibromatous / ossifying epulis (peripheral odontogenic fibroma)

locally aggressive basal cell carcinoma (BCC) (Acanthomatous ameloblastoma)

Question 18

Peripheral Odontogenic Fibroma (POF)

Answer 18

The most common oral tumour in the dog

Typically affects middle aged to older dogs of any breed.

Brachycephalic dogs such as boxers may be prone to developing multiple epuli.

These tumours are rare in the cat.

The aetiology is not known.

Question 19

Presentation of Peripheral Odontogenic Fibroma (POF)

Answer 19

This tumour presents as a firm - hard mass usually with a smooth, non-ulcerated surface.

It is firmly attached to the gingiva and periosteum of the dental arcade and grows outward, often from a relatively narrow base.

Question 20

Pathology of Peripheral Odontogenic Fibroma (POF)

Answer 20

Tumours show varying degrees of mineralisation, leading to the arbitary distinction between the fibromatous and ossifying forms.

The term peripheral odontogenic fibroma has been proposed to encompass both types on the basis that although they contain elements of odontogenic epithelium, they appear to be of mesenchymal origin.

Question 21

Behaviour of Peripheral Odontogenic Fibroma (POF)

Answer 21

Clinically these tumours are benign, they never invade into the adjacent bone and never metastasise.

Question 22

Treatment of Peripheral Odontogenic Fibroma (POF)

Answer 22

The treatment of choice is local surgical excision.

Resection of alveolar bone at the base of the mass may be necessary to effect a complete removal but the prognosis is excellent.

Question 23

Acanthomatous epulis / ameloblastoma, Basal Cell Carcinoma (BCC)

Answer 23

Tumours occur principally in middle-aged dogs, although are occasionally reported in younger animals.

Medium to large breeds tend to be affected, there might be a male predilection.

The aetiology is not known.

Question 24

Presentation of Acanthomatous epulis / ameloblastoma, Basal Cell Carcinoma (BCC)

Answer 24

The gross appearance of this tumour is variable, it may present as an irregular, fungating epithelial mass or may be more invasive with an ulcerated appearance and occasionally contains areas of necrosis.

Radiographically there is usually lysis of adjacent alveolar bone and displacement or loss of teeth is common.

Occasionally the soft tissue of the tumour becomes mineralised.

Question 25

Pathology of Acanthomatous epulis / ameloblastoma, Basal Cell Carcinoma (BCC)

Answer 25

The term basal cell carcinoma has been applied to this tumour on the basis that the lesion is predominantly composed of clumps of basal epithelium attached to and apparently originating from the stratum germanitivum of the overlying gum.

The consistent infiltration into bone being characteristic of the behaviour of a carcinoma.

Question 26

Behaviour of Acanthomatous epulis / ameloblastoma, Basal Cell Carcinoma (BCC)

Answer 26

a locally aggressive tumour and invariably invades the adjacent alveolar bone.

does not metastasise, it does present a clinical problem by virtue of the invasive pattern of growth.

Question 27

Treatment of Acanthomatous epulis / ameloblastoma, Basal Cell Carcinoma (BCC)

Answer 27

wide local excision including a margin of at least 1 cm of alveolar bone beyond the gross or radiographic limit of the tumour.

radio-sensitive and high cure rates can also be achieved by radiotherapy .

However, surgery is the preferred treatment because there is a risk of the subsequent development of malignant tumours at the site of irradiated tumour

Question 28

Ameloblastoma

Answer 28

a rare dental tumour which arises from odontogenic epithelium.

Typically it occurs in young animals

In dogs the mandible is the usual site whereas a fibromatous form of ameloblastoma appears to be more frequent in the maxilla of young cats, especially the region of the upper canine.

Question 29

Presentation of ameloblastoma

Answer 29

At either site the expansive growth of the tumour results in gross swelling and distortion of the bone.

The tumour is composed of well defined, large cystic cavities and thus has a characteristic multiloculate radiographic appearance

Question 30

Behaviour of ameloblastomas

Answer 30

Benign

Question 31

Treatment of ameloblastoma

Answer 31

can be cured by complete surgical resection.

There is some evidence that curretage of the bony cavities is sufficient to achieve local control.

Question 32

Malignant oral tumours

Answer 32

Squamous cell carcinoma

Fibrosarcoma and other sarcomas

(Osteosarcoma)

Malignant melanoma

Question 33

Squamous Cell Carcinoma (SCC)

Answer 33

the most common malignant oral tumour in the dog and cat.

In the dog it accounts for approximately 20 – 30% of malignant oral tumours and tends to occur in older animals (average 8 - 10 years) of medium to larger breeds.

There is no sex predilection.

In the cat, SCC accounts for 70% of malignant oral tumours, it also occurs in older animals (average age 10 years) with no sex predilection.

Question 34

Presentation of gingival SCC

Answer 34

may arise at any site in the upper and lower dental arcades.

usually begins at the gingival margin and its invasive growth leads to destruction of the peridontal tissues and loosening of the teeth.

The gross appearance is of an irregular, proliferative or ulcerative epithelial lesion.

often friable and haemorrhagic and secondary bacterial infection is common .

Invasion and lysis of adjacent bone occurs in over 70% of cases

Question 35

Behaviour of gingival SCC

Answer 35

low rate of metastasis

Tumours sited more caudally in the mouth and particularly those involving the caudal maxilla, tend to be more invasive and carry a worse prognosis.

a much more aggressive neoplasm in the cat and there is often severe, deep invasion of bone at the time of presentation.

Question 36

Treatment of gingival SCC

Answer 36

In the dog, surgery is the treatment of choice for early stage lesions particularly those affecting rostral areas of the mouth.

Wide local excision by maxillectomy or mandibulectomy as appropriate is frequently curative, and 1 year survival rates are in the order of 84%.

In cats the extent of the tumour often precludes surgery and even those tumours deemed operable carry a poor prognosis.

The outcome following radiotherapy is poor.

Question 37

Fibrosarcoma incidence

Answer 37

The third most common malignant tumour of the canine oral cavity representing 10 – 20 % of malignant tumours at this site.

Although fibrosarcoma is a common tumour in the cat, its incidence in the oral cavity is low (less than 20% of tumours at this site), sites of predeliction being the soft tissues of the head, trunk and limbs.

Question 38

Fibrosarcoma signalment

Answer 38

It tends to occur in younger dogs, the mean age of onset is 7.5 years but up to 25% occur in animals under 5 years of age.

There is a 2:1 male:female ratio and the Retriever breeds appear to suffer a particularly high incidence.

Question 39

Presentation of fibrosarcoma

Answer 39

In the dog it most commonly involves the upper dental arcade often extending dorsally and laterally into the paranasal region and medially onto the palate.

firm, smooth mass with a broad base and in its early stages may be difficult to distinguish on gross inspection from gingival hyperplasia or POF.

Radiographic evidence of bone involvement is common in more advanced tumours but in general fibrosarcoma tends to cause less lysis than SCC or BCC and is more often associated with a proliferative periosteal reaction.

Question 40

Behaviour of fibrosarcoma

Answer 40

The histological appearance of fibrosarcoma of the oral cavity does not always correlate well with the biological behaviour of the tumour.

Some tumours may appear histologically low grade and yet show a very aggressive and infiltrating behaviour.

Local and distant metastasis occurs in around 25% of cases but the prognosis is always guarded due to the extensive infiltration of adjacent tissues.

Question 41

Treatment of fibrosarcoma

Answer 41

No single form of treatment has been found to be entirely effective.

Wide local surgical excision by mandibulectomy and maxillectomy may control early stage, low grade tumours but even such aggressive surgery does not achieve the compartmental type of resection which is necessary to erradicate most oral fibrosarcomas and one year survival rates with surgery alone are about 50%.

Not particularly sensitive to radiation and radiotherapy alone does not appear to offer any significant improvement in local tumour control over surgery.

However, the combination of surgery with radiation has been shown to improve the initial tumour response and extend patient survival but local recurrence can still occur.

Question 42

Undifferentiated sarcomas in the oral cavity

Answer 42

A number of less well differentiated sarcomas including haemangiosarcoma, spindle cell sarcomas and anaplastic sarcomas may also arise in the oral cavity of the dog.

As a group these tumours respresent 10- 20% of canine malignant oral tumours.

Question 43

Presentation of undifferentiated sarcomas

Answer 43

In gross appearance they may resemble fibrosarcoma but in many cases they are more aggressive tumours and present as a rapidly growing mass which may be friable or haemorrhagic and contain areas of necrosis.

Question 44

Behaviour of undifferentiated sarcomas

Answer 44

characterised by an infiltrative pattern of growth and are often locally advanced by the time of diagnosis.

A higher proportion of these tumours metastasise, usually via the haematogenous route to the lungs and other internal organs

Question 45

Treatment of undifferentiated sarcomas

Answer 45

The principles of management are essentially as for fibrosarcoma although the prognosis is often worse due to the rapid growth rate and higher risk of distant metastases.

Small early stage tumours may be surgically resected and, although most soft tissue sarcomas are not very radioresponsive, cytoreductive surgery combined with radiation therapy can be beneficial in the management of the more advanced tumours.

Question 46

Osteosarcomas in the oral cavity

Answer 46

Mainly locally infiltrative - rate of metastasis low - moderate

Surgical management bast

Not very radiosensitive or chemosensitive

Adjunctive, post-op RT not shown to be of benefit

Question 47

Melanoma incidence

Answer 47

Malignant melanomas represent about 30 – 40% of malignant tumours of the oral cavity in the dog. Oral melanoma is rare in the cat.

Question 48

Melanoma signalment

Answer 48

In the dog oral melanomas characteristically develop in older animals, the average age is 9 - 12 years.

There appears to be a sex predilection with male dogs affected four times more frequently than bitches.

Certain breeds of dog, particularly those with pigmented oral mucosa e.g. poodle, pug and cocker spaniel, may be predisposed to this tumour.

Question 49

Presentation of melanoma

Answer 49

Common sites in order of prevalence are the gums (especially in the region of the molar teeth), the labial mucosa and the hard palate.

rapidly growing friable and haemorrhagic soft tissue mass.

The degree of pigmentation varies considerably.

Secondary bacterial infection and necrosis may be present.

Invasion of the bone is less common in oral melanoma than with SCC and fibrosarcoma

Question 50

Melanoma behaviour

Answer 50

amongst the most malignant neoplasms encountered in companion animals.

Irrespective of local tumour control, the major problem presented by melanoma is the high incidence of both regional (nodal) and distant metastasis.

Question 51

Treatment of melanoma (Oral)

Answer 51

Local control can be achieved by wide surgical resection where the site of the tumour is appropriate or by radiotherapy.

respond to hypofractionated radiotherapy with local response rates approaching 70%.

In the absence of an effective method for the prevention or treatment of disseminated melanoma the prognosis for these tumours is poor and survival rates are in the order of 3 - 6 months.

Question 52

Summary of tuours of the oral cavity

Answer 52

Relatively common in cats and dogs

SCC most common in cats, prognosis usually poor

SCC, sarcoma, and melanoma main DDx in dogs, prognosis depends on site and stage but melanoma is very metastatic

Question 53

Tumours of the tongue

Answer 53

Tumours of the tongue are not common in either the cat or the dog but squamous cell carcinoma is the most common histological type of tumour at this site in both species.

Question 54

Presentation of lingual tumours

Answer 54

often painful and interfere with the function of the tongue.

Difficulties in prehension, mastication and drinking

Excessive salivation (often purulent or blood-tinged)

Halitosis.

Lack of grooming in cats

Question 55

Lingual tumour behaviour

Answer 55

SCC of the tongue is a particularly aggressive neoplasm which is characterised by rapid extension and invasion into the tongue such that the tumour often involves the full thickness of the tongue by the time of presentation.

Lymphatic invasion and metastasis are common.

Question 56

Treatment of lingual tumours

Answer 56

Surgery is the treatment of choice

Dogs will tolerate partial glossectomy involving up to 50 percent of the tongue quite well

but in the case of lingual SCC the extensive infiltration of the tongue at the time of presentation often precludes surgical resection.

the tongue is very sensitive to radiation toxicity so radiotherapy has not been a successful treatment

There have been some reports of chemotherapeutic treatment of lingual SCC in dogs and cats with drugs such as cisplatin (not cats), mitoxantrone and doxorubicin but chemotherapy has not become established as an effective treatment for such tumours.

Question 57

Prognosis for lingual SCC

Answer 57

Overall the prognosis for lingual SCC in both dogs and cats is poor.

In dogs where complete surgical resection is possible 1 year survival rates may exceed 50% but such cases are not common and 1 year survival rates are usually less than 25%.

Question 58

Tonsilar tumours

Answer 58

Squamous cell carcinoma is the most common tumour to affect the tonsil in dogs and cats.

Other tumours which may arise in the tonsil include:
· Lymphoma (usually as part of multicentric lymphoma)
· Metastatic tumours from the oral cavity, especially malignant melanoma.

Tonsillar SCC is less common than the gingival form in the dog and cat

Question 59

Aetiology of tonsillar SCC

Answer 59

Associations with environmental pollutants have been implied

Question 60

Signalment of tonsillar SCC

Answer 60

In the dog the average age of onset of the disease is 9 - 10 years and males are affected three times more often than bitches.

SCC of the tonsil is rare in the cat.

Question 61

Clinical signs of tonsillar

Answer 61

Usually a unilateral lesion

Early cases tonsil is a relatively normal size but has small papillomatous growths

Dysphagia

Difficulty swallowing

Gagging

Hypersalivation

Weight loss

Temporal muscle atrophy

Question 62

Tonsillar SCC behaviour

Answer 62

Locally aggressive

High rate of metastasis to retropharyngeal and cervical LNs

Haematological dissemination may also occur

Question 63

Treatment for tonsillar SCC

Answer 63

Results of surgery/radiotherapy/both are usually poor

No effective chemo

Prognosis bad

Question 64

Craniomandibular osteopathy

Answer 64

an important differential diagnosis for a bony swelling of the mandible but in contrast to osteosarcoma

usually occurs in juveniles, less than 1 year of age,

usually affects both mandibles, although lesions not necessarily bilaterally symmetrical

strongly breed associated and occurs particularly in West Highland White and Cairn Terriers, although it can arise in other breeds e.g. dobermann.

Question 65

Nasopharyngeal polyp

Answer 65

not true neoplasms but inflammatory lesions originating from the middle ear or eustachian tube in young (usually < 2 year old) cats.

No breed or sex predilection is known.

Polyps may grow into the external ear canal where they can be seen as a pink, fleshy mass but most grow via a pedicle into the pharynx

Question 66

Clinical signs of nasal polyps

Answer 66

Stridor / stertor / difficulty breathing

Change in voice

Sneezing

Swallowing problems

Rhinitis

Horner’s syndrome (associated with otitis media)

Question 67

Diagnosis of nasal polyps

Answer 67

May be seen as soft tissue masses on radiographs of the pharynx or visualised by retraction of the soft palate

Question 68

Treatment of nasopharyngeal polyps

Answer 68

Most nasopharyngeal polys can be removed by traction.

If an underlying cause can be identified (eg Middle ear disease) then this should be treated appropriately to prevent recurrence.

Question 69

Osteosarcoma of the skull

Answer 69

less common than that of the long bones in dogs.

There are two distinct variants of osteosarcoma which affect the bones of the canine skull
· Multilobular osteoma/ chondroma / Osteochondrosarcoma / Chondroma rodens
· Mandibular osteosarcoma.

Question 70

Multilobular osteochondrosarcoma

Answer 70

uncommon tumour which primarily occurs in older, medium to large breed dogs.

relatively slowly growing tumour

usually affects the bones of the calvarium.

Question 71

Signs and diagnosis of multilobular osteochondrosarcoma

Answer 71

Enlarging mass which is hard and fixed

Characteristic radiographic appearance of dense bony mass of nodular or stippled density

Question 72

Behaviour of multilobular osteochondrosarcoma

Answer 72

locally invasive and may cause lysis of underlying bone

Question 73

Treatment of multilobular osteochondrosarcoma

Answer 73

Surgical resection is the only effective treatment but complete surgical removal of the tumour may be difficult or impossible.

Question 74

Mandibular osteosarcoma

Answer 74

May arise in the ramus of the mandible

one of the five most common tumours of the mandible of dog

Question 75

Treatment of mandibular osteosarcoma

Answer 75

often possible to control primary tumour by hemimandibulectomy
- usually compartmental resection

Rapid metastasis is not a feature of tumours at this site