Oral Tumors

Unfortunately, oral cancer is common in our pets, with 6%-10% of all feline tumors and 5% of all canine tumors occurring in the mouth, making it the mouth the 4thmost common location for tumors. Oral cancer can be aggressive, and our best treatment approach involves early identification and surgical removal of the tumor. With H.VDOS, we can perform a variety of surgeries to completely or partially remove the tumor, depending on its type and severity.

Below we will review the following:

• Benign vs Malignant Tumors
• Tumor Biologic Behavior:
  • Site Predilection
  • Local Invasion
  • Metastasis
• Staging Oral Tumors
• Diagnostic Tests for Oral Tumors:
  • Fine Needle Aspirate with Cytology (FNAC)
  • Incisional Biopsy
  • Excisional Biopsy
  • Imaging (Radiographs, Ultrasound, & CT)
• Oral Tumor Treatment Options:
  • Surgical Treatment:
    • Surgical Debulking
    • Marginal Excision
    • Wide Excision
    • Radical Excision
  • Chemotherapy
  • Radiation Therapy
  • Immunotherapy
• Oral Tumors in Cats:
  • Fibrosarcoma (FSA)
  • Pyogenic Granuloma
  • Squamous Cell Carcinoma (SCC)
• Oral Tumors in Dogs:
  • Canine Acanthomatous Ameloblastoma (CAA)
  • Fibrosarcoma (FSA)
    & High-Low Fibrosarcoma (H/L FSA)
  • Malignant Melanoma (MM)
  • Peripheral Odontogenic Fibroma (POF)
  • Squamous Cell Carcinoma (SCC)
    & Canine Papillary Squamous Cell Carcinoma (PSCC)

There are generally 2 types of growths or masses that can develop in the body: benign tumors and malignant tumors. The key differences between malignant and benign tumors lie in their potential for invasion, metastasis, and threat to overall health.

• Non-cancerous growths.
• Typically grow slowly and remain localized, without spreading to other parts of the body.
• While they may cause symptoms depending on their location, they do not invade nearby tissues or metastasize.
• Usually not life-threatening, but may require treatment if they cause discomfort or other complications.

• Cancerous growths.
• Characterized by uncontrolled cell growth and division, often spreading into surrounding tissues (invasion), and potentially metastasizing to other parts of the body through the bloodstream or lymphatic system.
• Can be life-threatening if left untreated, disrupting normal organ function and spreading to vital organs.

The biological behavior of a tumor consists of site predilection, the ability to locally invade other tissues, and the ability to metastasize to other distant parts of the body.

• Refers to the tendency of certain types of tumors or cancers to occur more frequently in specific locations within the body.
• Influenced by factors such as tissue type, genetic predispositions, environmental exposures, and lifestyle factors.
• Crucial for diagnosis, treatment planning, and prognosis, allowing veterinarians to tailor screening, diagnostic approaches, and treatment accordingly.

• Refers to the process by which cancerous cells proliferate and spread into nearby tissues or organs, disrupting their normal structure and function.
• Characteristic of malignant tumors, distinguishing them from benign tumors, which typically remain confined to their site of origin.
• Can cause various clinical manifestations depending on the affected site.
• Understanding the extent of local invasion is crucial for staging cancer and determining appropriate treatment strategies.

• Refers to the spread of cancer cells from the primary tumor site to other parts of the body, forming secondary tumors in distant organs or tissues.
• Hallmark of malignant tumors and significantly affects prognosis.
• Involves cancer cells detaching from the primary tumor, invading surrounding tissues, entering the bloodstream or lymphatic system, and settling in distant sites to form new tumors.
• Understanding and targeting metastasis is essential for cancer treatment and management, often involving a combination of surgical, chemotherapy, radiation therapy, targeted therapy, or immunotherapy approaches.
• Common sites for evaluating metastatic disease include lymph nodes, lungs, and abdominal organs via various diagnostic techniques such as fine needle aspirate, radiographs, computed tomography (CT), and ultrasound.

Fine Needle Aspirate with Cytology (FNAC) is a minimally invasive diagnostic procedure commonly used to obtain a sample of cells or fluid from a suspicious mass or lesion for microscopic examination. This technique involves inserting a thin needle into the tumor or lesion and extracting a small amount of tissue or fluid. FNAC is widely utilized in both human and veterinary medicine to aid in the diagnosis of various types of tumors and lesions. 

• Procedure: FNAC involves using a thin needle to aspirate cells or fluid from the suspected tumor or lesion. The collected material is then smeared onto slides and examined under a microscope by a clinical pathologist to assess cell morphology and characteristics.
• Sample Size: FNAC provides a small sample of cells or fluid, which may limit the ability to evaluate tissue architecture and certain characteristics of the tumor.
• Diagnostic Information: FNAC can provide valuable preliminary diagnostic information, including tumor type, presence of malignancy, and sometimes tumor grade. However, it may not always provide definitive answers, and additional testing or biopsy may be necessary for confirmation.
• Advantages: FNAC is quick, relatively inexpensive, and minimally invasive. It can be performed in outpatient settings and often does not require sedation or anesthesia.
• Indications: FNAC is often considered for testing regional lymph nodes, especially when enlarged and/or painful, its utility in diagnosing primary oral tumors is limited due to potential infection, inflammation, and necrosis. These factors can lead to false-negative results stemming from the small sample size and random distribution of tumor cells.

Incisional biopsies are a crucial 1st step in assessing the biological behavior of an oral tumor. Even when excisional surgery is anticipated as the best treatment for the pet, an initial incisional biopsy aids in determining appropriate surgical margins. Large incisional biopsies are often necessary to obtain a sufficient sample, particularly as tumors are frequently infected, inflamed, and necrotic. Our goal is to obtain a representative sample without exacerbating morbidity and without complicating the definitive treatment of the tumor.

• Procedure: A small portion of the tumor or abnormal tissue is surgically removed via scalpel, biopsy forceps, or punch biopsy.
• Sample Size: Incisional biopsies provide a larger tissue sample compared to FNAC, allowing for a more comprehensive evaluation of tumor characteristics, including tissue architecture, invasiveness, and margins.
• Diagnostic Information: Incisional biopsies yield more detailed diagnostic information compared to FNAC, as they provide a larger and more representative tissue sample. They can help in determining tumor type, grade, extent of invasion, and other important characteristics.
• Risks: Incisional biopsies carry risks such as bleeding, infection, and damage to surrounding structures. Careful consideration is needed to balance the diagnostic benefits with the potential risks of the procedure.

Excisional biopsies are performed when complete removal of the tumor is feasible and safe, allowing for definitive diagnosis and potential treatment in a single procedure. This is a good option for small and superficial masses, where the probability of a benign tumor is high. Furthermore, even if an incisional biopsy has been previously conducted, the excised tissue for definitive surgical treatment is also submitted for biopsy. This serves to evaluate whether the tumor was completely removed and to provide the most accurate assessment of the tumor's biological behavior for subsequent follow-up care and monitoring.

• Procedure: The entire tumor or abnormal tissue is surgically removed along with a margin of healthy surrounding tissue. 
• Sample Size: Excisional biopsies provide the most comprehensive tissue sample, including the entire tumor and surrounding tissue. This allows for a thorough evaluation of tumor characteristics and margins.
• Diagnostic Information: Excisional biopsies offer the highest diagnostic yield, as they provide a complete specimen for examination. They are particularly useful for determining tumor type, grade, margins, and involvement of adjacent structures. 
• Risks: While excisional biopsies offer advantages in terms of diagnostic accuracy, they may carry a higher risk of complications compared to incisional biopsies, particularly if the tumor is large or located in a critical anatomical area.

Radiographs, ultrasound, and computed tomography (CT) scans are all valuable imaging modalities used in the staging of tumors, each offering unique advantages and limitations. Here's a comparison of these imaging techniques:

Radiographs (X-Rays Pictures):

• Advantages:
  • Widely available and relatively inexpensive.
  • Provides a quick and easy assessment of the size, location, and density of tumors.
  • Useful for evaluating lungs and bony structures, and detecting mineralization within tumors.
• Limitations:
  • Limited soft tissue detail compared to other imaging modalities.
  • Less sensitive for detecting small or subtle abnormalities.
  • Cannot differentiate between different types of soft tissue structures or characterize tumor composition.

Ultrasound:

• Advantages:
  • Non-invasive and does not involve ionizing radiation.
  • Provides real-time imaging, allowing for dynamic evaluation of structures.
  • Excellent for assessing soft tissue structures, such as organs and blood vessels.
  • Can differentiate between cystic and solid components within tumors.
• Limitations:
  • Operator-dependent, with image quality influenced by the skill and experience of the sonographer.
  • Limited penetration depth, making it less effective for evaluating deep-seated tumors or structures obscured by gas or bone.
  • Less detailed than CT for evaluating fine anatomical structures.

Computed Tomography (CT) Scans:

• Advantages:
  • Offers high-resolution, cross-sectional imaging of the entire body.
  • Provides excellent soft tissue contrast and detailed anatomical information.
  • Particularly useful for assessing the extent of tumor involvement, detecting metastases, and evaluating lymph nodes.
• Limitations:
  • Involves ionizing radiation.
  • Can require the use of contrast agents, which can be adverse to patients with preexisting kidney disease.
  • More expensive and less widely available than radiographs or ultrasound.
  • Required heavy sedation and/or general anesthesia in pets.

• Mechanism of Action: Surgical treatment involves the physical removal of the tumor and surrounding tissue, aiming to achieve complete resection and eliminate the primary source of cancer.
• Indications: Surgical treatment is often indicated for localized tumors that are amenable to resection, especially those with well-defined borders and minimal risk of metastasis.
• Advantages: Surgical treatment offers the potential for complete tumor removal and immediate symptomatic relief. It can also provide a definitive diagnosis through histopathological examination of the resected tissue.
• Limitations: Surgical treatment may not be suitable for tumors that are unresectable due to size, location, or involvement of critical structures. Additionally, it may carry risks such as surgical complications, functional impairment, and potential for tumor recurrence.

Surgical Debulking:

• Procedure: Debulking involves the partial removal of a tumor, reducing its size without necessarily aiming for complete excision.
• Goal: The primary goal of debulking is to alleviate symptoms caused by tumor mass effect, such as compression of adjacent structures or organs.
• Indications: Debulking may be considered when complete removal of the tumor is not feasible due to factors such as tumor size, location, or involvement of critical structures.
• Outcome: While debulking can improve symptoms and quality of life, it will not provide a definitive cure, and residual tumor tissue may continue to grow or recur over time. It is important to note that debulking aggressive oral masses is generally unrewarding. In fact, in some cases, debulking may cause more morbidity than doing nothing, due to a lack of normal healing of tumor tissue & increased bleeding from the debulked site.

Marginal Excision:

• Procedure: Marginal excision involves the removal of the tumor along with a narrow margin of surrounding normal tissue.
• Goal: The goal of marginal excision is to completely remove the visible tumor while preserving surrounding structures and function to the greatest extent possible.
• Indications: Marginal excision may be appropriate for tumors that are well-defined and easily delineated from surrounding tissues, with minimal risk of infiltration into adjacent structures.
• Outcome: Marginal excision aims to achieve local tumor control and reduce the risk of tumor recurrence while minimizing functional impairment or morbidity associated with surgery.

Wide Excision:

• Procedure: Wide excision involves the removal of the tumor along with a surrounding margin of normal tissue, typically ranging from 1 to 2 centimeters.
• Goal: The primary goal of wide excision is to achieve complete removal of the tumor along with any microscopic extensions or satellite lesions, reducing the risk of local recurrence.
• Indications: Wide excision is often used for tumors with a higher risk of local recurrence or infiltration into adjacent structures, requiring a more aggressive surgical approach.
• Outcome: Wide excision aims to provide adequate margins of resection to ensure complete tumor removal while minimizing the risk of leaving behind residual tumor cells.

Radical Excision:

• Procedure: Radical excision involves the removal of the tumor along with a wide margin of surrounding tissue, including any adjacent structures or organs that may be involved or at risk of involvement.
• Goal: The goal of radical excision is to achieve complete tumor removal while also addressing any potential microscopic extensions or metastases, often at the expense of sacrificing adjacent structures or organs.
• Indications: Radical excision is reserved for tumors with aggressive biological behavior, extensive local invasion, or involvement of critical structures where preservation of function may be secondary to achieving oncological clearance.
• Outcome: Radical excision aims to provide the best chance of long-term disease control and survival, albeit with a higher risk of functional impairment or morbidity associated with more extensive surgery.
• In summary, the choice of surgical approach depends on various factors, including the characteristics of the tumor, its location, biological behavior, and the goals of treatment, balancing the need for the complete tumor removal with preservation of function and minimizing morbidity.

• Mechanism of Action: Chemotherapy involves the administration of cytotoxic drugs that target rapidly dividing cancer cells, inhibiting their growth or causing cell death.
• Indications: Chemotherapy is often used as systemic treatment for tumors that have metastasized or are at high risk of recurrence. It can also be used as neoadjuvant therapy to shrink tumors before surgery or as adjuvant therapy to reduce the risk of recurrence after surgery.
• Advantages: Chemotherapy has the potential to target cancer cells throughout the body, making it effective against metastatic disease. It can be used in combination with other treatment modalities to improve outcomes.
• Limitations: Chemotherapy can cause significant side effects, including nausea, vomiting, hair loss, immunosuppression, and increased risk of infections. It may also lead to drug resistance and limited efficacy in certain tumor types.

• Mechanism of Action: Radiation therapy delivers high-energy radiation to target and destroy cancer cells, either by directly damaging DNA or inducing cell death through apoptosis or necrosis.
• Indications: Radiation therapy is used as a primary treatment for localized tumors that are not amenable to surgery or as adjuvant therapy after surgery to reduce the risk of local recurrence. It can also be used palliatively to relieve symptoms in advanced or metastatic disease.
• Advantages: Radiation therapy offers precise targeting of tumor tissue while sparing surrounding normal tissues. It can be delivered externally (external beam radiation) or internally (brachytherapy), depending on the tumor location and characteristics.
• Limitations: Radiation therapy can cause acute and late toxicities, including radiation dermatitis, mucositis, fatigue, and radiation-induced fibrosis. Previously irradiated tissue can be less amenable to surgical treatment in the future.

• Mechanism of Action: Immunotherapy harnesses the body's immune system to recognize and attack cancer cells, either by boosting immune responses or inhibiting immune checkpoints that prevent immune cells from recognizing and destroying tumors.
• Indications: Immunotherapy is indicated for certain types of tumors, particularly those with high levels of immune infiltration or expression of specific immune targets. It has shown promising results in various cancers, including melanoma.
• Advantages: Immunotherapy offers the potential for durable responses and long-term disease control, with fewer systemic side effects compared to chemotherapy.
• Limitations: Immunotherapy may cause immune-related adverse events, including inflammation of normal tissues and organs. Response rates can vary widely among patients, and not all tumors are responsive to immunotherapy.

Oral tumors in cats represent approximately 3%-10% of feline tumors. Among these, squamous cell carcinoma (SCC) stands out as the most prevalent malignant tumor, representing 60%-70% of cases, followed by fibrosarcoma (FSA).

Oral fibrosarcoma (FSA) is the 2nd most common oral tumor in cats, with an incidence ranging from 13%-17%. These tumors are locally invasive, often infiltrating the gingiva and bone; local recurrence after surgical removal is frequent. Although FSA can metastasize, it rarely spreads to regional lymph nodes, and lung metastasis occurs in less than 20% of cases. Surgery is the primary treatment modality and prioritizing local control is paramount, given that local recurrence is the most common cause of death. Radiation therapy can be used alone or in combination with surgery, although its role is generally palliative. 

Pyogenic granulomas, also known as chewing or traumatic granulomas, are reactive lesions of the gingiva or mucosa in cats. Despite its name, it doesn't involve bacteria and isn't truly granulomatous. It occurs in response to trauma and is characterized by exuberant connective tissue growth. Pyogenic granulomas typically occur on the outside surface of the mandibular (lower) 1st molar teeth in cats. This is often caused by trauma from the maxillary (upper) 4th premolar tooth, possibly due to a subtle malocclusion. Surgical excision combined with removal of the underlying cause is curative. For cases caused by contact with the maxillary fourth premolar, treatment involves either crown reduction or extraction of that tooth.

Oral squamous cell carcinoma (SCC) is the most common type of oral tumor in cats, accounting for approximately 75% of all oral tumors and 60%-70% of malignant feline oral tumors. While the exact cause is not fully understood, potential risk factors include certain dietary components (such as canned tuna and cat food), exposure to tobacco smoke, flea collars, and periodontal disease. While some viruses were previously thought to play a role, their significance is now uncertain. These tumors often exhibit local invasion into bone and surrounding tissues. Metastasis, while historically considered low and late in the disease course, may occur in regional lymph nodes, although distant metastasis is rare. Treatment options for oral SCC include surgery, radiation therapy, and chemotherapy. Surgery aims to remove the tumor with sufficient margins, while radiation therapy can be effective in improving survival rates, especially when combined with other treatments. Chemotherapy may be used, although there is no single effective chemotherapeutic agent for SCC. Unfortunately, the prognosis for cats with oral SCC is generally poor, with a low long-term survival rate and mean survival time ranging from 3-14 months, depending on the treatment approach. Despite the challenges, certain treatment combinations, such as radiation therapy combined with surgery, may offer longer survival times in some cases.

Oral tumors in dogs represent about 6% of all canine tumors and rank as the fourth most common location for cancer in dogs. Malignant melanoma (MM) tops the list as the most frequent oral tumor in dogs, followed by squamous cell carcinoma (SCC), which constitutes 17% to 25% of all canine oral tumors, and fibrosarcoma (FSA).

Canine acanthomatous ameloblastoma (CAA) is a distinct subtype of oral tumor commonly found in dogs. While sharing some histological features with human ameloblastomas, its biological behavior and radiological characteristics are unique to dogs. CAA is prevalent among middle-aged dogs, typically around 8-9 years old. There is no clear sex predilection, although certain breeds like Akitas, Cocker Spaniels, Golden Retrievers, and Shetland Sheepdogs may be more predisposed. This tumor is commonly located in the rostral mandible (front lower jaw). Surgery remains the primary treatment for CAA, with complete surgical excision, especially with clean margins, offering a good to excellent prognosis. In some cases, intralesional bleomycin or radiation therapy may be employed, although results can vary due to differences in tumor biology.

Oral fibrosarcoma (FSA) ranks as the 3rdmost common oral tumor in dogs. This condition typically affects middle-aged to older, large-breed dogs. FSA is characterized by its locally aggressive nature with maxillary and palatal lesions being more prevalent, often leading to bone involvement. Metastasis, while rare, tends to occur late in the disease progression. Treatment typically involves surgery, such as mandibulectomy or maxillectomy, although recurrences are common. Radiation therapy, while often palliative, can be used in conjunction with surgery. Chemotherapy options are limited and poorly responsive. Local control is paramount, as local recurrence is the primary cause of mortality. High-grade FSA carries a higher risk of metastasis compared to low-grade lesions. Surgical resection, especially mandibulectomy, may offer survival benefits, with adjuvant therapies providing additional support.

High-Low Fibrosarcoma (H/L FSA):

High-low fibrosarcoma (H/L FSA) is a type of fibrosarcoma seen predominantly in large-breed dogs, particularly Golden Retrievers. Despite its histologically low-grade appearance, it exhibits aggressive biological behavior, requiring a proactive approach to management. While metastasis is rare, it can occur, most commonly spreads to the lungs and regional lymph nodes. Aggressive surgical intervention is crucial, involving wide resection margins of at least 2 cm. However, complete excision is challenging due to the infiltrative nature of the tumor. Radical surgery, possibly followed by radiation therapy, offers the best chance for a cure. Radiation therapy alone or in combination with surgery may be considered, although it is generally less effective. Early diagnosis and aggressive treatment significantly impact survival outcomes. Prolonged survival can be achieved with various treatment modalities, including surgery, radiation therapy, and multimodal approaches. Unfortunately, existing grading schemes have limited prognostic value in predicting outcomes for oral soft tissue sarcomas like H/L FSA.

Oral malignant melanoma (MM), while rare in humans, is the most common oral and maxillofacial tumor in dogs. It more commonly affects older male dogs. While certain breeds may have a predisposition, there is no clear breed specificity. MM is highly aggressive, it often shows local invasion into bone and has a variable metastatic rate, commonly spreading to lymph nodes, lungs, liver, and the central nervous system. Treatment options include surgery, radiation therapy, chemotherapy, and immunotherapy. Surgery with aggressive margins is associated with longer disease-free intervals and survival times. Radiation therapy, particularly when surgery is not feasible, can provide palliative benefits. Chemotherapy and immunotherapy have shown some efficacy, especially in conjunction with other treatments. Prognosis varies widely depending on factors such as tumor size, stage, and histologic features. Generally, smaller tumors without metastasis have better outcomes. Despite treatment, the prognosis for MM remains guarded to poor due to its aggressive nature and high metastatic rate.

Peripheral odontogenic fibromas (POF) are a type of oral tumor found in dogs. It originates from the periodontal ligament, gingiva, or underlying periosteum near the cementoenamel junction. POF’s can affect dogs of any age, sex, or breed. There are no specific predispositions based on these factors. Unlike some other oral tumors, POF does not exhibit invasive features. Radiographically, it typically appears as a soft tissue swelling without involvement of underlying alveolar bone, except in cases of secondary periodontitis. Surgery is the mainstay of treatment for POF. Local marginal excision, with particular attention to removing the entire lesion down to the affected periosteum, is often curative. In some cases, tooth extraction or en bloc resection of the tumor and associated teeth may be necessary. The prognosis for POF is generally good with complete excision. However, recurrence is possible if the entire lesion is not removed. More aggressive treatments may be considered for recurrent or broad-based lesions.

Oral squamous cell carcinoma (SCC) is the second most common type of oral tumor in dogs, accounting for 17%-25% of all oral tumors. Its occurrence varies between rural and urban areas, with higher frequencies observed in urban settings, suggesting a potential environmental influence such as air pollution. SCC arises from the oral mucosa and is associated with chronic gingivitis, periodontitis, and possibly canine papillomavirus. While SCC can affect dogs of any age and sex, it is more commonly seen in larger breeds and slightly younger dogs, with a mean age of 8-10 years. This cancer typically affects the mandible and maxilla equally, with common sites including maxillary (upper) molar teeth. This tumor tends to locally invade surrounding tissues and has variable metastatic rates, with regional lymph node and distant metastasis being more common in lingual and tonsillar SCC. Treatment options for SCC include surgery, radiation therapy, chemotherapy, and photodynamic therapy. Surgery aims to achieve 1 cm surgical margins, with procedures such as mandibulectomy or maxillectomy often employed. Radiation therapy is effective, with median disease-free intervals of 36 months and median survival times of 14-16 months. Chemotherapy, particularly using piroxicam or cisplatin combined with piroxicam, has shown some response rates but may be associated with renal toxicity. Photodynamic therapy using photosensitizers has also been investigated, showing promising results in some cases.

Canine Papillary Squamous Cell Carcinoma (PSCC):

Papillary squamous cell carcinoma (PSCC) is a rare type of cancer in dogs originating from odontogenic tissue. While initially thought to primarily affect young dogs, it has been found in adult dogs as well, with certain breeds being more predisposed, although no specific breed predilection has been established. Diagnosis often involves biopsy, though it's noted that initial biopsies may yield misdiagnoses, emphasizing the importance of deep bone biopsies. Imaging, particularly CT scans, can aid in the diagnosis. Treatment options include surgery and radiation therapy. Megavoltage radiation therapy has shown efficacy, especially in younger dogs, although early radiation therapy may affect bone growth and cause facial malformations. The prognosis for PSCC in dogs, especially those under 6 years old, can be relatively good if the tumor is completely resected. The long-term prognosis remains unclear due to limited reported cases, highlighting the need for continued research and monitoring. Regular diagnostic imaging is advisable even after apparent successful treatment to monitor for any signs of recurrence.