basuki, w - approach to oral tumors

Proceedings of VetFest 2020 Basuki, W - Approach to oral tumours

Approach to oral tumours Dr. Williana Basuki, BVSc (Hons), MS, MANZCVS, DAVDC

Adjunct Associate Professor, Cummings School of Veterinary Medicine, Tufts University Tufts Veterinary Emergency Treatment and Specialties

525 South Street, Walpole, MA, 02081, USA Introduction The term “tumour” can be defined as a tissue growth due to accumulation of abnormal cells and the interpretation of the term has been associated with a neoplastic process which can be either benign or malignant.1 Benign oral neoplasia can be invasive or non-invasive to the local region, but they do not metastasise to other organ systems. On the other hand, regional and distant lymph node involvement and metastasis are usually associated with malignant oral tumours along with their invasiveness to the affected area. Oral tumours are frequently noted as an incidental finding by the clinician during a routine veterinary visit. It is also common for an oral tumour to be found by the client when its appearance or size is significant. The client may also notice some halitosis, facial structure distortion, bleeding or difficulty eating. Along with a detailed history, thorough clinical examination that includes physical and oral examinations is one of the most important steps in appropriately diagnosing an oral tumour. The findings of our clinical examination may allow us to narrow down and further discuss the differential diagnosis with the clients and guide them in choosing the appropriate diagnostic work up to achieve an accurate diagnosis. In this proceeding, we will discuss our approach to oral tumours that includes clinical examination, diagnostic imaging, and biopsy technique. Clinical Examination and Diagnostic Imaging Based on the staging system described by the World Health Organization, there are three basic elements in staging the extent of tumour involvement (Table 1): primary tumour (T), regional lymph node (N), metastasis (M). It is recommended to utilise this staging system to systematically approach an oral tumour. At the time of first presentation, a full physical examination will need to be performed along with a thorough conscious oral exam. The oral tumour needs to be evaluated closely during this step. Approximate measurement, appearance, consistency, size and invasiveness of the oral tumour need to be evaluated.1-3 Any associated teeth need to be assessed for potential mobility and displacement. In addition, any potential bone or regional structure involvement such as the nasal cavity will need to be assessed. If known, the growth rate of the oral tumour will need to be recorded as this information can be useful in determining the nature of the oral tumour. All of these steps will need to be repeated when the patient is anesthetized for more accurate information. A complete blood count, serum, biochemistry profile, and urinalysis are recommended to be performed prior to anesthetising the patient and as part of a routine and standard health screening. Regional lymph nodes such as parotid and mandibular lymph nodes need to be palpated during both conscious and anesthetized oral exams to assess their involvement. The assessment of the medial retropharyngeal lymph nodes may be challenging due to their deep location in the neck region and their involvement may only be evaluated via CT scan.1,2 When the lymph nodes are suspected to be involved, a fine needle aspirate with cytology analysis need to be performed as palpation or size evaluation is known to be poorly sensitive and poorly specific in detecting metastasis (an enlarged lymph node does not necessarily mean evidence of metastasis as it can also be a reactive lymph

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node).1,4 A study also reported that only 17% of palpably enlarged mandibular lymph nodes in dogs and cats with oral tumours were found to contain metastasis.5 Diagnostic imaging such as intraoral dental radiography and CT are crucial in oral tumour cases. The tumour characteristic and invasiveness can be assessed using dental radiography. It is important to remember that radiographic evidence of bony lysis or changes only becomes evident when more than 40% of the cortical bone has demineralized.3 Skull radiographs may not be useful in evaluating oral tumours due to the anatomical superimposition of the maxillary and mandibular structures. Computed Tomography (CT) of the skull provides a higher value in evaluating the extent of oral tumours to the surrounding region especially when the TMJ, nasal, sinus, and periorbital regions are suspected to be involved.2 CT-guided biopsy may also be performed if the tumour is seated in deep structures and aids in surgical planning.1,2 In addition, the regional lymph nodes can be evaluated using CT. I don’t routinely perform thoracic radiographs or CT scan and/or abdominal ultrasound for metastatic screening on the same day of my anesthetized oral exam. Commonly, I perform the anesthetized oral exam and the tumour biopsy along with the diagnostic imaging relevant to evaluating the oral tumour such as intraoral dental radiography and/or CT scan of the skull. My decision on this is based on multiple different factors and discussion with the clients during the first examination. For example, I will recommend an anesthetized oral exam, biopsy, and intraoral dental radiography and/or CT of the skull to further evaluate the tumour if it appears to be benign (e.g. non-ulcerated, smooth-marginated, small, non-pigmented, no apparent growth) and the owner prefers to obtain the diagnosis prior to committing further financially. On the other hand, I will discuss with the clients and highly recommend the metastasis screening to be done on the same day if the appearance of the oral tumour is concerning for malignancy (e.g. ulcerated, friable, pigmented, bleeding, appeared to be invasive or involving the surrounding bone). This additional discussion and recommendation are important especially if the evidence of metastasis will change the client’s decision on the patient’s management following the biopsy results, e.g. surgical resection vs. further referral to a veterinary oncologist for chemotherapy and/or radiation therapy vs. palliative care). Other clinicians may have different opinions on this matter. In addition, it is important to remember that the type of tumour cannot be determined solely based on its clinical and diagnostic imaging (even if it has benign appearance), and biopsy needs to be performed to achieve a definitive diagnosis. Biopsy Obtaining a biopsy sample of the oral tumour and histopathological analysis are considered the current gold standard in getting an accurate diagnosis in oral tumour cases. Performing a biopsy does not require a complex or advanced technical skill; however, it is important for clinicians to carefully plan and consider all factors prior to performing a biopsy as there are potential complications and adverse effects to patient prognosis associated with a poorly performed biopsy. In the human literature, the maximum pain intensity associated with biopsy procedure was reported to be 2 hours post-op and the swelling appeared between 6 and 48 hours after biopsy.6 Therefore, it is recommended to perform a regional nerve block (such as infraorbital or inferior alveolar block) prior to biopsy and post-operative pain management will need to be prescribed.1,2,6 Regional nerve block should not be done if its administration increases the risk of seeding or spreading cancer cells into other anatomical structures. Whenever possible, an incisional biopsy should be performed to obtain a tissue sample of the oral tumour for further histopathologic analysis. This method is preferable to an excisional biopsy as it minimizes the risk of contaminating the surrounding region with any cancer cells which may affect the extent of the surgical margin once the definitive diagnosis is obtained. An excisional biopsy can

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be performed if the oral tumour is small, pedunculated, and its removal does not affect the treatment option.2 In addition, oral tumours should be biopsied through the oral cavity directly and not from the skin surface to avoid contamination with cancer cells.1 The biopsy can be achieved by using a punch biopsy or scalpel blade (I routinely use a #15 scalpel blade). No electrocautery and laser should be used in obtaining mucosal lesions as these methods create coagulation artifacts which make the histopathologic interpretation more challenging. The sample needs to be at least 3mm in diameter and 2mm deep if a punch biopsy is used.2 Therefore, it is recommended to use a punch biopsy with 4-6mm diameter as the sample will shrink following formalin fixation.2 Ideally, the biopsy site should be sutured with 4-0 or 5-0 poliglecaprone 25 suture material in a simple interrupted suture pattern to achieve hemostasis.2,6 If not possible, haemostasis can be achieved by applying digital pressure with gauze. In general, a large (or multiple) biopsy sample is preferable for more accurate histopathologic interpretation. If only smaller samples can be obtained, multiple samples from different areas of the lesion may be required to obtain a diagnosis.1 In addition, areas of necrosis and/or ulceration need to be avoided and no normal tissues need to be included in the biopsy sample.6 The biopsy sample will need to be placed in a 10% neutral buffered formalin fixative with 20 times the volume of the sample A close rapport between the pathologist and clinician are important in achieving the accurate diagnosis in oral tumour cases. Upon submitting the biopsy sample, clinicians need to provide pertinent patient signalment, history, clinical description of the lesion that include its measurement, radiographic appearance, and biopsy method. It is also preferable and recommended for clinical photographs to be included in the submission. Direct communication between the clinician and pathologist may be required in certain challenging cases to streamline the diagnosis.

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Table 1. WHO clinical staging (TNM) of oral and maxillofacial tumours

T Primary tumour Tis Preinvasive carcinoma (carcinoma in situ) T0 No evidence of tumour T1 Tumour <20 mm maximum diameter T1a Without bone invasion T1b With bone invasion T2 Tumour 20–40 mm maximum diameter T2a Without bone invasion T2b With bone invasion T3 Tumour >40 mm diameter T3a Without bone invasion T3b With bone invasion

N Regional lymph node (RLN): superficial cervical, medial retropharyngeal, mandibular and parotid N0 No evidence of RLN involvement N1 Movable ipsilateral nodes N1a Nodes not considered to contain growth [histologically (−)] N1b Nodes considered to contain growth [histologically (+)] N2 Movable contralateral or bilateral nodes N2a Nodes not considered to contain growth [histologically (−)] N2b Nodes considered to contain growth [histologically (+)] N3 Fixed node

M Distant metastasis M0 No evidence of distant metastasis M1 Distant metastasis (including distant nodes)

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References

1. Reiter AM, Gracis M. BSAVA Manual of Canine and Feline Dentistry and Oral Surgery. Wiley; 2018.

2. Verstraete FJM, Lommer MJ, Arzi B. Oral and Maxillofacial Surgery in Dogs and Cats. Elsevier - Health Sciences Division; 2019.

3. Withrow SJ, MacEwan EG. Small animal clinical oncology. 3rd ed. ed. Philadelphia: Philadelphia : W. B. Saunders; 2001.

4. Williams LE, Packer RA. Association between lymph node size and metastasis in dogs with oral malignant melanoma: 100 cases (1987-2001). J Am Vet Med Assoc 2003;222(9):1234-1236.

5. Herring ES, Smith MM, Robertson JL. Lymph node staging of oral and maxillofacial neoplasms in 31 dogs and cats. J Vet Dent 2002;19(3):122-126.

6. Verstraete FJM, Lommer MJ, Bezuidenhout AJ. Oral and maxillofacial surgery in dogs and cats. Edinburgh: Saunders/Elsevier; 2012.

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basuki, w - approach to oral tumors

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