Tumours of the oral cavity

Tumours of the oral cavity account for 6% and 3% of all neoplasms in dogs and cats, respectively._^1,2 The types of possible tumours are extremely varied, and every part of the mouth can be affected. In dogs, the soft tissues can give rise to the following tumours, in decreasing order of incidence: malignant melanoma, squamous cell carcinoma and fibrosarcoma; epulides (benign gingival lesions) and oral papillomatosis have also been reported. Tumours derived from hard tissues can be divided into those originating from bone (osteosarcoma and, more rarely, other sarcomas) and those originating from dental tissues (the so-called odontogenic tumours, such as ameloblastoma, ameloblastic fibro-odontoma, odontoma, fibro-ameloblastoma and dental cysts). Finally, other, clinically less relevant tumours have also been reported. In general, males are more affected than females,_¹ especially in the case of tonsillar squamous cell carcinoma, malignant melanoma and fibrosarcoma. The benign tumours which can infiltrate bone tissue are acanthomatous epulis and ameloblastoma; all malignant tumours, sooner or later, infiltrate bone tissues. In cats, the malignant neoplasms include squamous cell carcinoma and sarcoma, and all may infiltrate bone tissues. Benign tumours, including epulides, are rare.

CLASSIFICATION

EPULIDES

Epulides originate from the periodontal ligament, are benign and are classified as follows: (i) fibromatous (Fig. 1), (ii) ossifying (Fig. 2), (iii) acanthomatous (Figs. 3A and B) and (iv) giant cell._¹ Although benign, all epulides may relapse if not appropriately treated; in any case, only acanthomatous epulis, and occasionally ossifying epulis with a broad base of attachment, require additional resection of the underlying bone (en bloc excision) (Figs. 4 A, B, C, D). In acantomathous epulis, which has a predilection for the rostral part of the two dental arches (Figs. 3A and 5), radiographically the bone also appears to be involved. Radiotherapy may be proposed as an alternative to surgery and provides control of the disease in at least 90% of cases. However, apart from radiation-induced osteonecrosis, up to 10% of cases of acanthomatous epulis treated with irradiation, especially if orthovoltage radiation is used (rare nowadays), may develop sarcomas or, more rarely, carcinomas at the irradiated sites, after a variable period of time._^5,6 Finally, local injection of bleomycin is another possible treatment._⁵²

Boxers, but also other brachiocephalic breeds and, occasionally, animals of other breeds, can develop multiple epulides, which may be interpreted as diffuse gingival hyperplasia (Fig. 6). In such cases a family predisposition may be considered. Cytoreductive surgery is indicated only when the lesions interfere with the intake of food and mastication. In the cat, in which acanthomatous epulis has not been reported, epulides are extremely rare and, if present, are often multiple (Figs. 7A and B) and, in 50% of cases,  occur in subjects under 3 years old._¹

MALIGNANT MELANOMA

Malignant melanoma accounts for 30-40% of all malignant tumours of the oral cavity in the dog._^1,2 The subjects which are most predisposed are small dogs, but also the Chow Chow and other large dogs (to a lesser extent), with intense mucosal pigmentation, and over 10-11 years old show a certain predisposition._^1,7,8  The prevalence seems higher in male dogs. Malignant melanoma can originate in any site of the oral cavity, including the tonsils (Fig. 8); gingival malignant melanoma is more frequent in the area of the inferior premolars (Figs. 9A, B and C) or superior molars (Fig. 10). These tumours are often ulcerated, bleed easily and are necrotic (causing halitosis); some are pedunculated or with a small base of attachment, especially on the cheek or at the mucocutaneous junction (Figs. 11A and B). The degree of pigmentation (melanotic, partially melanotic or amelanotic - Figs. 11 and 12A and B) is not a prognostic parameter. Amelanotic forms are, however, more difficult to recognize histologically, and frequently a diagnosis of undifferentiated, anaplastic, or even epithelial tumour is made._¹ Immunohistochemistry (Melan A) may be helpful, although the diagnostic problem remains in undifferentiated forms._⁸ Malignant melanoma is characterized by a rapid growth rate, early local bone invasion (increased  looseness and loss of teeth) and also a high rate of metastasis (to ipsilateral regional lymph nodes in up to 70-80% of cases, already at presentation, and also bilaterally in the case of aboral tumours; finally, to the lungs and to other organs) (Figs. 13A and B, 14A, B and C, 15])._¹ Metastasisation appears to be influenced by the site, size and clinical stage of the tumour._^1,9.10

The prognostic factors are size (over 2 cm or 8 cm_³), site (the prognosis is slightly more favourable for rostral malignant melanomas of the lower mandibular arch and for aboral ones of the maxillary arch) and mitotic index (< or > 3 mitoses per high-power field). Pedunculated malignant melanomas, as well as lingual malignant melanomas (of the aboral third - Figs. 16A and B) or of the  lips (Fig. 11), seem to have a lower metastatic index._¹ In these cases the  only really curative option, when possible and in selected cases (small tumour, regional lymph nodes not involved or with metastasis to only the first node station), is an en bloc resection of the tumour. Although combination with classical adjuvant treatments (radiotherapy, chemotherapy – in most cases with  cisplatin  or carboplatin) does improve local control of the tumour in up to 75% of cases, the survival rate at 1 year does not exceed 30%._^1,11,23  Recently, promising results have been achieved with immunotherapy. In the cat, oral malignant melanoma is extremely rare; the biological-clinical behaviour of the tumour is similar to that in the dog.

SQUAMOUS CELL CARCINOMA

Dog. Squamous cell carcinoma is the second most frequent malignant tumour. It occurs more commonly in medium-sized and large dogs. The average age at diagnosis is 8-10 years old, but it can also be found in younger subjects; there is no predisposition for gender or breed. Squamous cell carcinoma may originate from any site of the oral cavity, including the tonsils. In the case of gingival involvement there is apparently no correlation between periodontal diseases and tumour development; tonsillar tumours, on the other hand, are more frequent in subjects living in urban areas._¹ The lesions are friable, with a nodular, cauliflower or plaque-like appearance, and frequently have areas of necrosis and ulceration (Figs. 17A and B). The bone is infiltrated in around 75% of cases; this gives rise to increased looseness of the teeth, with consequent loss of one or more teeth (Figs. 18A, B, C and D). Tumours affecting the rostral part of the oral cavity (Fig. 18A) have a less aggressive behaviour (metastases to regional lymph nodes in 5-10% of cases, to the lungs in 3%): this means that en bloc resection of the tumour may be followed by a higher survival rate at 1 year (up to 90% in some studies)._¹ On the other hand, when aboral sites are affected the prognosis is less favourable, with the possibility of earlier metastases (in up to 90% of cases at first presentation for lingual (Figs. 19A, B and C, 64A and B) and tonsillar  (Figs. 20A, B, C, D and E) tumours._^1,8 Squamous cell carcinomas in other sites have an “intermediate” prognosis, depending on the site, size, degree of invasion and regional metastasisation. 

Squamous cell carcinoma is a particularly radiosensitive tumour, hence in inoperable cases radiotherapy may be used with a palliative intent. The use of chemotherapy is controversial, as the metastatic rate is usually not high; nevertheless, some studies have shown the possible usefulness of chemotherapy in non-tonsillar squamous cell carcinoma, also in combination with COX-2 inhibitors such as piroxicam._^22,28 This association is, however, extremely nephrotoxic.

Cat. Squamous cell carcinoma is the most common oral tumour in cats (70%); the risk of this tumour seems to be associated with the use of flea-control collars, exposure to_{cigarette smoke and the consumption of canned food (in particular fish-based products).²⁹ Affected cats are usually over 10 years old. Squamous cell carcinoma may originate from any site in the oral cavity, although localisation in the tonsils is rare. The behaviour of feline squamous cell carcinoma is similar to that of the canine tumour, although the degree of local invasion of the feline form, often with broad and deep ulcerations, is much more intense (tumour and secondary infection) (Figs. 21A and B). This invasion is demonstrable by radiology already at the initial evaluation in most cases, especially in the mandible, where there is often an intense periosteal reaction (to the extent of simulating a bone sarcoma - Figs. 22A, B and C). In almost all cases the extensive tissue destruction precludes the possibility of surgical excision. Ulcerations may be absent in “intra-alveolar” squamous cell carcinoma, an extremely rare tumour which probably originates from the dental lamina. The possibility of paraneoplastic hypercalcaemia has been reported in the literature.³⁰}

If surgery is not a realistic option (as is often the case), local control of the tumour with radiotherapy may be considered. This is not, however, possible when the squamous cell carcinoma originates from the base of the tongue (Figs. 23A and B). Unfortunately, in this case there are currently no really effective treatments; in exceptional cases (a favourable site) surgical resection is possible.

FIBROSARCOMA

Fibrosarcoma accounts for 10-20% of all malignant oral tumours in the dog (third in frequency after malignant melanoma and squamous cell carcinoma) and is second, in terms of frequency, in the cat._¹ The mean age of affected dogs is 7 years old, although around 25% of subjects are under 5 years old. This tumour mostly affects large, dolicocephalic, male dogs. It may develop in the gums, hard palate, tongue and labial mucosa. The gingival form is more often present in the maxillary arch, between the canine and the fourth premolar teeth (Figs. 24A, B and C]); in the mandibular arch the tumour is usually more rostral (Figs. 25A, B and C). The lesion is lardaceous, solid, pinkish, slow-growing, compact and only occasionally ulcerated. At times, in the initial stages, it may be pedunculated. The rate of local infiltration is high, but this is appreciable in bone only in advanced stages (Fig. 26). Histologically, the tumour may appear weakly or strongly malignant (the so-called “low” or “high” grade fibrosarcoma); from a biological point of view histologically low grade fibrosarcomas (at times diagnosed as “fibromas”) are still to be considered highly malignant (Fig. 27)._³¹ The metastatic rate, also to regional lymph nodes, is low (maximum 25-30% of cases)._^11,13,32,33

All the above implies that surgery of the tumour often requires “compartmental” resections, with broad margins of healthy tissue all around the neoplasm. Relapses are frequent (occurring in up to 60% of cases) and the 1-year survival rate in affected dogs is 40-50%._¹ Local control of the disease often requires adjuvant radiotherapy; in such cases median survival is 18-26 months and the 1-year survival rate is 76%._¹

In the cat, the biological characteristics and the sites affected by fibrosarcoma are similar to those in the dog (Figs. 28A and B); likewise, as in dogs surgery may be considered a realistic option only in a few cats.

OSTEOSARCOMA

In 10-15% of cases of osteosarcoma, the cranium and mandible are affected; both erosive and productive lesions are possible (Figs. 29A and B). Osteosarcoma preferentially occurs in medium-sized and large, middle-aged or elderly dogs, possibly with a slight prevalence in females; the tumour usually occurs in aboral sites, both in the maxilla and in the mandible (Fig. 30). Compared to the appendicular phenotype, oral osteosarcoma, if resectable en bloc, has a better prognosis and a lower tendency to metastasise (1-year survival rate of about 35-70%)._^1,11,13,34 For this reason adjuvant chemotherapy is not used. The critical factor is to be able to perform a radical excision with clean margins (complete hemimandibulectomy if the mandibular arch is affected); adjuvant radiotherapy and/or chemotherapy do not improve the prognosis.

Osteosarcoma is rare in the cat. If it can be resected en bloc, with clean margins (but unfortunately this does not happen frequently) the prognosis is favourable, in view of its limited metastatic rate, like that of the appendicular phenotype.

CANINE VIRAL PAPILLOMATOSIS 

Canine viral papillomatosis is manifested as a single or multiple, cauliflower-like excrescences and is caused by a horizontally transmitted, species-specific, DNA Papovavirus. Viral papillomatosis can occasionally evolve into a squamous cell carcinoma. Canine viral papillomatosis usually occurs in dogs under 1-year old, although older subjects may be affected occasionally (e.g. in the case of immunodepression for various reasons - (Fig. 31). Lesions typically affect the oral cavity (Figs. 32A and B), lips or eyelids. They usually resolve spontaneously in 1-3 months as a result of the evoked immune response._¹ In the past, autologous vaccines were used but the possibility of developing malignant cutaneous tumours at the vaccine inoculation site was reported._⁴ Furthermore, there are also reports of the development of pigmented plaques (in Miniature Schnauzer, Pomeranian and American Staffordshire Terrier breeds) which in some cases evolved into a squamous cell carcinoma._³⁵

ODONTOGENIC TUMOURS

Odontogenic tumours originate from the epithelium of the dental lamina; they are all benign and may contain different dental components. The most important tumour within this group is ameloblastoma (in the past confused with acanthomatous epulis)_³⁶ Ameloblastoma typically develops in middle-aged dogs, with a slight prevalence in medium-sized to large, male dogs; it is locally invasive (causing increased teeth looseness and localised loss of teeth), it does not metastasise and at radiography and computed tomography it may appear as single or multiple cysts (Figs. 33A and B, 34A and B). Clinically, it appears as a solid, irregular mass, covered by epithelium or with a more invasive and ulcerated form, with areas of necrosis (Fig. 35). The treatment of choice is en bloc resection, including removal of the underlying bone. Following excision with clean margins the prognosis is favourable. Other possible treatments include local injection of bleomycin and interleukin 12 with electroporation._^53,54

Rarer odontogenic tumours are odontoma, ameloblastic fibro-odontoma, inductive fibromeloblastoma*, calcifying epithelial odontogenic tumour of the cat and dentigerous cysts** (Figs. 36A and B); all these lesions are benign, with no tumour spread, and hence surgical removal, followed, if necessary, by grafting with autologous cancellous bone, is usually curative._¹ Radiotherapy is indicated for all bulky lesions.

RARER TUMOURS

Tumours which are less frequently encountered include granular cell myoblastoma*, juvenile tumours (sarcomas - Fig. 37 – or undifferentiated neoplasms, papillary squamous cell carcinoma, etc.),_¹ multilobular osteochondrosarcoma** (Figs. 38A, B and C),_^38,39 other mesenchymal tumours, round cell tumours (mast cell tumour, lymphoma, etc.) (Figs. 39A, B, C and D) and minor salivary gland tumours (extremely rare).

CLINICAL SIGNS

Patients with oral cavity tumours are often brought for a clinical examination when the lesion is already in an advanced stage of development. This happens because in the initial stages these tumours are often asymptomatic and not visible, especially if located in aboral sites. Halitosis (resulting from necrosis, ulceration and local infections) is intense, especially in malignant melanoma, but less so in squamous cell carcinoma. Bleeding, frank or mixed with saliva (sialorrhoea), can occur in animals with malignant melanoma and squamous cell carcinoma, as well as in those with other ulcerated tumours. In some maxillary tumours there can also be epiphora, due to involvement of the naso-lachrymal duct. In some cases the lesion is detected incidentally, for example during a dental cleaning procedure; in other cases it is found after spontaneous loss of one or more teeth. Tooth loss must always be viewed with suspicion (especially in the absence of evident peridontal disease in other sites) and requires an immediate biopsy. In more advanced stages the severity of the initial clinical signs depends on the site involved: for example, problems in opening the mouth, pain, and varying degrees of exophthalmos and/or deviation of the eyeball are characteristic of an invasion of the retro-bulbar space. Facial deformity of different degrees may also be evident. Dysphagia, rhinorrhoea and/or respiratory sounds (pharyngeal or nasal) have been reported in association with some aboral tumours and in the case of intranasal invasion (a negative prognostic factor if surgery alone is considered - Figs. 18A, B, C and D; 20A, B, C, D and E; 26). Sometimes owners report that the animal has difficulty with prehension of food (lingual tumours or large lesions). Finally, ipsilateral or, in the case of aboral lesions, also bilateral regional lymphadenopathy may sometimes become evident. The lymph nodes may be smooth and mobile (compatible with reactive phenomena) or already with evident features of neoplastic involvement (hard, irregular surface, tethered to a variable extent to the skin). Cervical lymphadenopathy may be the first evident clinical sign of squamous cell carcinoma of the tonsil.

DIAGNOSIS

The patient’s evaluation must include:

• Clinical history(especially any spontaneous loss or excessively easy extraction of individual teeth)
• Careful clinical examination. Inspection of the oral cavity (done under anaesthesia) usually allows a lesion to be detected. One important recommendation is not to make a diagnosis based only on the clinical examination (at most a tumour may only be suspected), as there are many lesions, in both dogs and cats, which may simulate a malignant oral tumour: eosinophilic granuloma (in the cat - Figs. 40A, B and C – and, more rarely, in the  dog* (Fig. 41),_^40-42 gingivitis/stomatitis/glossitis of different aetiologies (specific or non-specific infection), lymphoplasmacellular stomatitis (in the cat Fig. 42), dental and periodontal diseases, osteomyelitis of various causes (Fig. 43), mucosal leishmaniasis (in the dog), oral calcinosis circumscripta (usually affecting the tongue, at different sites - Fig. 44]), autoimmune diseases, various salivary gland disorders, retrobulbar diseases (Fig. 45), bone diseases (craniomandibular osteopathy of the dog - Fig. 46, osteodystrophies, etc.), rhinopharyngeal inflammatory polyps of the cat, abscesses (Figs. 47A and B), etc. Finally, it should be remembered that very different tumours (e.g. osteosarcoma, ossifying epulis and ameloblastoma) may sometimes present in a clinically similar way.

• Blood, blood-chemistry and urine tests. In the cat it is always appropriate to assess the animal’s Feline immunodeficiency virus and Feline leukemia virus status.
• Incisional biopsy of the oral lesion. If the patient is collaborative, or in the presence of exophytic lesions which are already ulcerated, the biopsy may be taken under simple sedation, otherwise (preferably) under anaesthesia. The biopsy can be taken from the centre or also from the periphery of the lesion (without however modifying planning of the subsequent treatment) and should be sufficiently deep (the superficial part of the lesion is in fact often infected, necrotic and ulcerated). The biopsy sample thus taken can undergo immediate cytological studies (by imprint or scarification) and then sent for histology. Fine needle aspiration biopsies of oral lesions are not usually taken because of the massive contamination by blood and inflammation/infection/necrosis which often complicates the cytological interpretation of the sample; it is also worth noting that the cell exfoliation of some tumours is minimal (fibrosarcoma, sarcomas in general, epulides, etc.). In some  lesions (e.g. fibromatous epulides, papillomas) excisional biopsies may already be considered as the final treatment.
• Fine needle aspiration biopsy of regional/satellite lymph  nodes (mandibular, parathyroid, medial retropharyngeal),_¹ particularly if enlarged. Lymph node enlargement does not, however, necessarily correspond to metastatic spread of the disease; in the same way,  negative cytology does not exclude  metastatic involvement and, especially for tumour staging, the lymph node/s is/are should be removed concomitantly with the excision of the primary tumour.
• Radiographic examination of the chest (right and left latero-lateral and dorso-ventral views, during inspiration): X-rays are carried out to exclude possible pulmonary metastatic dissemination (more probable in the case of malignant melanoma).
• Radiographic examination of the site of the primary lesion in all the views necessary (dorso-ventral, lateral, oblique, open mouth view, intraoral, etc.) with the purpose of detecting any lytic or osteoproductive bone involvement. Bone involvement is evident radiographically when the erosion affects at least 40% of the cortical bone._¹ This implies that, if histology confirms the diagnosis of a malignant tumour, the surgical excision must in any case also include the underlying bone, even in the absence of evident erosion.
• Computed tomography or  nuclear magnetic resonance imaging is necessary in most cases, in order to plan the best surgical intervention. These imaging studies are more sensitive than radiography for defining any retrobulbar, intranasal, etc. invasion. The examination should be extended to the neck (lymphoadenopathies – Fig. 48) and to the chest (lung metastases), especially in the case of biologically aggressive tumours.
• Ultrasonography of the abdomen. This is done only in selected cases and for particularly malignant tumours.
• Cardiologic examination, possibly including echocardiography (in elderly animals, especially large ones).

TREATMENT

The main pre-treatment prognostic factors to be considered are:

• Histological type: this corresponds to a specific biological-clinical behaviour of the tumour, which must be considered when planning the management. In the case of surgery, the histological type determines the extent of the resection needed.
• Site of the tumour: the site conditions the surgical accessibility. In general, rostral tumours are more easily accessible than aboral tumours; similarly, lesions that extend beyond the median sagittal plane are less amenable to surgery (because of problems with subsequent reconstruction).
• Tumour Node Metastasis (TNM) clinical staging (WHO)_⁹. The TNM classification incorporates information on: (i) tumour size (the T parameter, which influences both the possibility of surgery – which also depends on the size of the animal– and the tendency of the tumour to spread – e.g. in the case of malignant melanoma): (ii) the status of regional lymph nodes (the N parameter; even with negative cytology in the case of a malignant tumour the lymph nodes of the first station should be excised together with the primary lesion, and assessed histologically; if the tumour is in an aboral site it is preferable to remove the regional lymph nodes on both sides; in general, in the case of positivity of the first lymph node station patients may still be considered as “surgical” candidates; (iii) presence of distant metastases (the M parameter, metastases in the second or subsequent lymph node stations or in distant organs; if present, treatment can only be palliative).
• General physical condition of the patient. This is an obvious factor, as only clinically “healthy” patients, independently of age, should be considered as candidates for treatment.

The treatment modalities which are more commonly used are surgery and radiotherapy. Historically, cryosurgery was indicated for squamous cell tumours smaller than 1-2 cm, although this technique is very rarely used nowadays.

En bloc surgery is advisable for all malignant neoplasms that can be removed; furthermore, it is a valid option, and also cheaper than radiotherapy, for large, benign lesions. In the case of malignant tumours, independently of whether or not there is evidence of bone involvement, the bone must always be included in the ‘en bloc’ resection (other treatments). In cases in which surgery could cause an unacceptable loss of function, the alternatives are radiotherapy (more often) and/or chemotherapy (more rarely), in a palliative (Figs. 49A, B and C) or adjuvant setting.

In this context, adjuvant radiotherapy is used following less radical excision, in which there is a greater risk of the margins not being completely clear of tumour (Figs. 50A, B, and C); the purpose of adjuvant chemotherapy, on the other hand, is to limit metastatic dissemination. Radiotherapy can be used successfully in radiosensitive tumours, such as acanthomatous epulis, squamous cell carcinoma and, albeit to a lesser extent, ameloblastoma; radiotherapy can also be used as an adjuvant in the case of fibrosarcoma and squamous cell carcinoma and as palliative therapy in inoperable squamous cell carcinoma, fibrosarcoma and malignant melanoma. Radiosensitising agents  (cisplatin, carboplatin, gemcitabine, etc.) may be used together with radiotherapy; in the case of malignant melanoma the use of fractionated high doses, administered in a few sessions, may improve local control of the disease.

Classical chemotherapy, as well as COX-2 inhibitors (alone or in combination with platinum salts, for both squamous cell carcinomas and malignant melanomas), have not yet found a precise indication._{^{15,18,22,23,28}}  In the case of malignant melanoma, vaccination is also possible._^24-27

SURGERY

Possible surgical interventions are mandibulectomy and maxillectomy; other operations may be used for the soft tissues (tonsils, tongue, lips, cheek, etc.). The essential surgical instrumentation includes, apart from the normal instruments for soft tissues, a hammer and scalpels, bone forceps and an oscillating saw. In the case of malignant tumours, the excision margins should be at least 2 cm; this is rarely feasible in the cat (because the lesions are usually too advanced). In the case of doubt, or if problems with prehension of food and/or various types of complications in the post-operative period are expected, it is advisable to end the surgery with placement of an oesophageal tube (Figs. 51A and B), in order to facilitate management of the patient and to allow the animal to learn to eat per os again, once adjusted to the new situation.

With regards to mandibular arch tumours, the possible interventions are:_{^{1,11,30,33,43-47}}

• Unilateral or bilateral mandibulectomy (Figs. 52A and B; Figs. 53A and B).

• • Segmental or complete horizontal mandibulectomy (Figs. 55A and B; Fig. 56).

• Vertical mandibulectomy (see Fig. 57).

• Hemimandibulectomy (Figs. 57A, B,C, D; E and F).

With regards to maxillary arch tumours, the possible operations include removal of variable parts of maxillary, incisor, palatine, nasal and lachrymal bone and the zygomatic arch. The remaining bone must be sufficient to guarantee structural stability and patency of the respiratory tract, without the need for prosthetic implants. In the dog, in the case of very extensive maxillary resection, temporary ligation of the two common carotid arteries (in the cervical area, with a ventral sagittal approach) may be indicated in order to limit intra-operative bleeding (especially in large subjects) (Figs. 58A and B)._^48,49 More specifically, the possible interventions are:_{^{1,13,45-47,50,51}}

• Unilateral or bilateral premaxillectomy (Figs. 50 and 59A, B, C and D).

• Central maxillectomy (Fig. 60).

• Caudal maxillectomy (Figs. 61A and B)

• Nasal maxillectomy (Figs. 62A and B).

• Hemimaxillectomy (Figs. 63A and B)

OTHER OPERATIONS

1. Lingual resection. Lingual resection is possible (Figs. 64A  and B). The prognosis depends on the histological type of the tumour, its size, the site involved and the presence of any metastases (specifically to regional lymph nodes).
2. Resections of the cheek and lips. After en bloc resection special reconstructive procedures are often necessary to fill in the defect (advancement or transposition flaps, rope flaps, axial flaps, etc.).
3. Special operations.In selected cases, and if the lesion is benign, the instruments for tibial plateau levelling osteotomy can be used for oral osteotomy. This strategy is much less destructive (Figs. 65A and B).

Once the surgery has been completed, besides histological studies of the regional lymph nodes (for tumour staging and prognostication), it is essential to evaluate the excision margins of the primary tumour (e.g. with India ink - Fig. 66 – or stitches), in order to determine histologically that the excision has been complete.

Post-operative management

In most cases, soft food may be administeredper os 24-48 hours after surgery. It is always advisable to use an Elyzabethan collar for at least 1 week. Broad-spectrum antibiotic prophylaxis is usually administered for 5-7 days. It is worth recalling again that an oesophageal tube should be placed at the end of surgery following extremely extensive resections and/or if complications are expected. In such cases, in the days following surgery soft food can be administered both through the tube and per os, until the problem has resolved (meaning that the subject returns to eating food only per os). The administration of soft food is usually continued for the first 2-3 months after surgery.

Complications of surgery

The most frequent surgical complications, some of which are inevitable, are:

1. Intra-operative haemorrhage (especially in the case of maxillectomy). This may be prevented and controlled by ligation of the common carotid arteries and/or blood transfusions.
2. Post-operatorive epistaxis (in the case of maxillary resections): this is usually self-limiting and resolves in 3-5 days.
3. Wound dehiscence and development of oronasal fistulae.
4. Infections: although by definition this is “contaminated” surgery, infections are rare.
5. Mandibular deviations and alterations of occlusion.
6. Excessive salivation and prolapse of the tongue (Fig. 69)
7. Epiphora caused by sectioning, elimination or ligation of the naso-lachrymal duct.
8. Oedema or “false ranula” of the lateral aspect of the tongue, following a segmental or horizontal mandibulectomy or a total hemimandibulectomy (especially in the cat and, in the dog, in the case of incisions close to the ventral aspect of the tongue).
9. Ranula (following horizontal or rostral bilateral mandibular resections after the third premolar tooth): usually the problem resolves within a few days. The use of non-steroidal anti-inflammatory drugs is helpful.
10. Function.
11. Aesthetic result.

In the dog, en bloc resection with clean margins may be curative in almost all acanthomatous epulides and ameloblastomas, and in most rostral squamous cell carcinomas. In the case of aboral squamous cell carcinomas (especially tonsillar), the prognosis is poor, and surgery should be considered to be only palliative. The 1-year survival rate is 40-50% in the case of fibrosarcoma, up to 70% for osteosarcoma and up to 30% in dogs with selected malignant melanomas.

In the cat, the number of operations that can be carried out is more limited because of the considerable aggressiveness (tumour + infection) of most squamous cell carcinomas and because the tumours frequently involve the tongue. However, in the selected cases in which resection with clean margins is a realistic possibility, survival can be extended. For other neoplastic phenotypes the results are similar to those in the dog although, unfortunately, most cats are inoperable already at presentation.

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