6 The cancer patient with halitosis and/or hypersalivation
Hypersalivation and/or halitosis in a cancer patient are usually signs of an intraoral neoplasm and as such, these clinical signs are frequently accompanied by a poor appetite or complete anorexia, especially in the cat. However, drooling saliva may also be indicative of encephalopathy, especially in the cat, which can be caused by hepatic neoplasia, or possibly by an intracranial mass. Oral cancers are considered to be quite common in veterinary medicine, being reported to be the fourth most common malignancy type seen in clinical practice, accounting for 6% of all canine tumours and 3% of all feline tumours. In dogs, the most common tumour type seen is malignant melanoma, followed by squamous cell carcinoma and then fibrosarcoma, whereas in cats, squamous cell carcinomas are the most common, followed by fibrosarcoma. However, many other tumour types have been reported in the literature and a careful histological analysis is required to ensure an accurate diagnosis is made in every case.
The submandibular lymph node was enlarged but cytological evaluation of fine needle aspirates revealed this to be due to a reactive lymphadenopathy with no evidence of metastatic disease. In the light of the degree of bony swelling, there was concern that there may be significant tumour invasion into the underlying bone, so an MRI scan was performed (Fig. 6.3). This revealed that the mass had indeed invaded through the nasal bone into the nasal cavity and had actually crossed the midline.
It was felt that the intranasal extension of the tumour indicated that it would not be possible to undertake surgery with curative intent as it would not be possible to obtain clean margins. The oral mass, therefore, was biopsied to see whether or not radiotherapy was a viable treatment option. The histopathology returned to show the mass was a squamous cell carcinoma and as the owners did not want surgery anyway, radiotherapy was offered as the sole treatment. The dog underwent a hypofractionated radiotherapy course as previously described. The swelling reduced in size and the owner’s concern with blood in the water bowl stopped for 7 months, but then it returned along with right-sided unilateral serosanguineous discharge and the dog was euthanized 2 months later.
Many patients with an oral tumour will present because the owner has found a mass within the mouth, but tumours located caudally within the oral cavity or sublingually may be difficult to see. These cases can present with a variety of clinical signs. Drooling saliva that may or may not be blood-tinged, worsening halitosis, dysphagia or progressively worsening inappetance are all potentially consistent with an oral tumour and warrant a careful and thorough oral examination. The index of suspicion may rise further depending on the signalment of the patient; male dogs have a greater risk of developing an oral tumour compared to female dogs and there are certain breeds (e.g. cocker spaniels, German shepherd dogs, German short-haired pointers, Weimaraners, golden retrievers and boxers) that are reported to have an increased risk of developing oral cancers. Furthermore, large-breed dogs have a higher incidence of fibrosarcomas and non-tonsillar squamous cell carcinomas whilst small-breed dogs show an increased incidence of malignant melanoma and tonsillar carcinoma. Benign lesions such as papillomatosis are more common in younger dogs.
A careful oral examination must obviously be performed, even if this requires sedation or a brief anaesthetic to ensure all areas of the oral cavity (including underneath the tongue and in the fauces) have been visualized and examined. In addition to a careful oral examination, attention must be paid to careful palpation of the submandibular lymph nodes and the general condition of the patient, as many oral tumours will have metastatic potential and the possibility of distant disease must always be considered. Some studies have shown that for highly metastatic tumours such as oral melanoma, a significant percentage of cases will have lymph node involvement despite being palpably normal. So if a melanoma is suspected and the primary mass can be excised, excision of the draining submandibular lymph node(s) is also useful from a staging perspective, although no studies have shown such a procedure generates any favourable prognostic advantage compared to leaving the node behind.
In view of the different possible diagnoses and the treatment and prognostic implications of such differences, it is essential to make a definitive histopathological diagnosis by biopsy. Prior to any surgery (biopsy or excision procedure) for an oral mass, left and right inflated lateral thoracic radiographs must be obtained to rule out the presence of visible metastases, as indicated in the section above. Local radiography at the site of the lesion is also strongly recommended to investigate the degree of bony involvement. It is important to remember, however, that an apparently normal radiograph does not rule out bone invasion as there has to be up to 40% bone lysis before a lesion will be visible radiographically. Advanced imaging techniques (particularly CT but also MRI) are more sensitive tools to evaluate the extent of disease and/or the presence of bone lesions and patients should be referred for such investigations when possible or necessary. Being able to accurately plan which treatment or treatment combinations are most appropriate for the patient before there has been an attempt at excisional surgery significantly improves the likelihood of success and reduces stress and discomfort, whilst frequently reducing the overall cost of the treatment required.
Once a full staging process has been completed, a biopsy procedure or specific treatment can be planned depending on the outcome of these investigations. The correct treatment may vary depending on the diagnosis and clinical stage reached, so incisional biopsy at surgery remains the first-line method to diagnose the exact nature of most oral tumours (Figs 6.4, 6.5). If it is decided to attempt excisional biopsy, the important fact to remember is that for many oral tumours (with the exceptions of fibrous and ossifying epulides) there is a significant risk of invasion into the adjacent jaw bone, so surgical resection should include bony margins to increase the likelihood of achieving good local control. It is for this reason that it is often sensible to obtain an accurate diagnosis by obtaining an incisional biopsy before attempting excisional surgery. Cats, but especially dogs, generally tolerate partial maxillectomy, mandibulectomy or orbitectomy well and the cosmetic outcomes are good, although this should be discussed with clients carefully beforehand.
Figure 6.4 An acanthomatous epulis located on the caudal mandible of a dog. Clinical staging indicated that there was no distant disease and the dog was treated with a partial mandibulectomy with good functional results and no tumour recurrence 2 years later
With regard to specific treatment, surgery is usually the most appropriate course of action required for oral neoplasia. Exactly what surgical procedure will be required depends upon the tumour type, the tumour size and the tumour location but it is recommended to try to achieve 2-cm margins (including of the underlying bone) if the mass is confirmed to be malignant. Local segmental excision to include the underlying bone is indicated for all small oral tumours (except ossifying and fibromatous epulides) but larger tumours will require more extensive surgery such as hemimandibulectomy, hemimaxillectomy or orbitectomy procedures (Tables 6.1, 6.2).
The immediate postoperative recovery for canine patients who undergo more aggressive or extensive surgery is usually still rapid with most eating well the evening after their surgery and it is, therefore, not usual for feeding tubes to be placed in the dog (Figs 6.6-6.15).
Figure 6.6 One of the more common cosmetic changes in a dog who has undergone a partial mandibulectomy: lateral protrusion of the tongue. Occasionally the jaw will move laterally and may cause the lower canine tooth to impinge on the hard palate