Introduction

The incidence of tongue tumours in domestic animals is infrequent and probably not more than 4% of tumours affecting the oral cavity and pharyngeal area. Epidemiological studies of lingual tumours in dogs¹ and cats are scarce². Since tongue tumours are infrequently encountered, the author is doing a review of the literature and describing the most commonly diagnosed lingual tumours of dogs and cats with guidelines on treatment.

Clinical Presentation

The clinical signs associated with lingual tumours may be determined by the extent of the tumour. In approximately 25% of cases lingual tumours are usually discovered as an incidental finding; however, a combination of the following clinical signs may usually be present:^3-5

 Hypersalivation/ptyalism

 Dysphagia

 Inappetance

 Noisy respirations

 Haemorrhage

 Visible tumour

 Coughing

 Vomiting

Diagnostic Protocol

Evaluation (TNM)

The staging and classification of any oncological patient is essential for prognostication and treatment planning. There exists different systems for oral carcinomas and sarcomas and clinicians should be aware of this when dealing with a patient.

Haematology and Biochemistry

In the workup of a patient it is good practice to take samples for general haematology and serum chemistry. Not only does this help to establish pre-treatment values, it also helps to ascertain the systemic health of the patient.

Diagnostic Imaging

A combination of diagnostic imaging modalities may be used to evaluate the patient. Ultrasonography can be useful to evaluate the base of the tongue as well as the abdominal organs (metastases). Computed tomography combined with a contrast agent can be most useful to delineate the tumour and help expose affected local lymph nodes.

Biopsy

Incisional biopsies of the tongue can be performed by using a scalpel blade or using a biopsy punch. The tongue is comprised of muscle and therefore has a good blood supply that can be adequately controlled by occlusion at the base of the tongue with fingers or by applying digital pressure at the biopsy site.

Tumours of the Canine Tongue

Table 1. The following malignant and benign neoplasia have been reported in the literature as cited

*Squamous cell carcinoma is the most common neoplasm diagnosed in these studies. **Melanoma is the most common neoplasm in these studies.

Tumours of the Feline Tongue

In cats, squamous cell carcinoma (SCC) is by far the most common tumour type seen in the oral cavity and especially the tongue.^2,6,7 The average age of cats developing lingual SCC is slightly lower (11.9 years) compared to cats developing oral SCC (13.6 years).⁶ Other lingual neoplasia in the cat is rare indeed and apart from lymphoma⁸ and granular cell tumours⁹ absent in the literature.

Treatment Options

The final treatment plan will depend on several parameters that should all be taken in to account. Some of these are:

 Systemic health of patient

 Site of tumour

 Histological diagnosis of tumour

 Metastases of tumour

 Tumour sensitive to radiation or chemotherapy

 Cost implications for owner

 Access to radiation/photodynamic therapy

 Skill and preference of clinician

Surgery

For most tumours (excluding lymphoma), surgical removal of the tumour is still the mainstay for therapy. A classification for glossectomies has been described for dogs based on a human classification system:¹⁰

Partial Glossectomy

Excision or amputation of any part of the oral (free) portion of the tongue, rostral to the frenulum.

Subtotal Glossectomy

Excision or amputation of the entire free portion of the tongue as well as a portion of either the genioglossus or geniohyoid muscles or both. This extends caudal to the frenulum.

Near Total Glossectomy

A resection of ≥ 75% of the entire tongue.

Total Glossectomy

Amputation or excision of the entire tongue.

Gaining tumour-free margins remains the biggest challenge for the surgeon. Local regrowth is common where this was not attained.³

Chemotherapy

There are currently no standardised protocols for adjuvant or neoadjuvant therapy in addition to surgery. Chemotherapy is not frequently used yet and efforts should be made to standardise protocols in the future to determine the value of these for patients with lingual neoplasia.³ Current advice will rely on the protocols for similar tumours in other parts of the body.

Radiation

Radiation of especially SCC in the tongues of dogs and cats can be considered as an adjunct therapy. In a recent study, cats tolerated radiation of oral SCC and in T1 animals it extended the progression-free survival time by a median of 590 days.¹¹

Photodynamic Therapy (PDT)

Photodynamic therapy for the treatment of oral and then specifically lingual carcinomas is being developed. It is important that clinicians should understand that PDT is a 2-stage procedure. Firstly, a patient is injected with a photosensitising agent and then, light therapy is applied after a period of time that is dependent on the photosensitiser used. This therapy shows much promise in humans and will hopefully be developed further for use in animals as well. Clinicians not familiar with this kind of therapy should refrain from using it until they have been trained in this procedure, as it may have serious complications like oral inflammation if used incorrectly.

References

1.  Dennis MM, Ehrhart N, Duncan CG, Barnes AB, Ehrhart EJ. Frequency of and risk factors associated with lingual lesions in dogs: 1,196 cases (1995–2004). Journal of the American Veterinary Medical Association. 2006;228(10):1533–1537.

2.  Bastianello SS. A survey of neoplasia in domestic species over a 40-year period from 1935 to 1974 in the Republic of South Africa. V. Tumours occurring in the cat. The Onderstepoort Journal of Veterinary Research. 1983;50(2):105–110.

3.  Culp WT, Ehrhart N, Withrow SJ, Rebhun RB, Boston S, Buracco P, et al. Results of surgical excision and evaluation of factors associated with survival time in dogs with lingual neoplasia: 97 cases (1995–2008). Journal of the American Veterinary Medical Association. 2013;242(10):1392–1397.

4.  Beck EB, Withrow SJ, McChesney AE, Richardson RC, Henderson RA, Norris AM, et al. Canine tongue tumours: A retrospective review of 57 cases. Journal of the American Animal Hospital Association. 1986;22:525–532.

5.  Syrcle JA, Bonczynski JJ, Monette S, Bergman PJ. Retrospective evaluation of lingual tumors in 42 dogs: 1999–2005. Journal of the American Animal Hospital Association. 2008;44(6):308–319.

6.  Martin CK, Tannehill-Gregg SH, Wolfe TD, Rosol TJ. Bone-invasive oral squamous cell carcinoma in cats: pathology and expression of parathyroid hormone-related protein. Veterinary Pathology. 2011;48(1):302–312.

7.  Levene A. Upper digestive tract neoplasia in the cat (a comparative study). The Journal of Laryngology and Otology. 1984;98(12):1221–1223.

8.  Bound NJ, Priestnall SL, Cariou MP. Lingual and renal lymphoma in a cat. Journal of Feline Medicine and Surgery. 2011;13(4):272–275.

9.  Patnaik AK. Histologic and immunohistochemical studies of granular cell tumors in seven dogs, three cats, one horse, and one bird. Veterinary Pathology. 1993;30(2):176–185.

10. Dvorak LD, Beaver DP, Ellison GW, Bellah JR, Mann FA, Henry CJ. Major glossectomy in dogs: a case series and proposed classification system. Journal of the American Animal Hospital Association. 2004;40(4):331–337.

11. Poirier VJ, Kaser-Hotz B, Vail DM, Straw RC. Efficacy and toxicity of an accelerated hypofractionated radiation therapy protocol in cats with oral squamous cell carcinoma. Veterinary Radiology & Ultrasound. 2013;54(1):81–88.