Oral and Nasal Squamous Cell Carcinoma in Dogs

Oral and Nasal Squamous Cell Carcinoma in Dogs

The squamous cell carcinoma is often one of the most heart-breaking tumors any living being can develop. The tumor is rapidly invasive locally but does not spread in the way we usually think of a cancer spreading until late in its course. This would seem to be a positive aspect lending itself to potential surgical removal and cure, but unfortunately that’s usually not the case. The tumor tends to arise in locations where surgery is challenging or where the tumor isn’t detectable until surgery is no longer possible. 
Before reviewing some of the more classical presentations of this tumor, let’s address what squamous cells are. Our bodies must interface with the outside world in several areas: our skin, our mouth and nose, our entire gastrointestinal tract, respiratory tract and even urinary and reproductive tracts. All these areas are accessible from the outside world, if not directly like the skin is, then via some sort of opening like the urinary or GI tract. The cells that line these are areas are called epithelial cells and they can take many shapes depending on whether their job is to protect us from the environment (skin), absorb material from the environment (GI tract), or perform some other sort of job (respiratory tract). Epithelial cells also line our body cavities, the outside of our organs and blood vessels, and form a thin casing.   
Squamous epithelial cells are flat plate-like cells that form layers, a sort of a microscopic armor against the wear and tear that comes from interfacing with the environment. The squamous cells make up the outer layer of the skin, nose, and mouth.   
The squamous cell carcinoma (sometimes called simply a squame) arises when the body’s squamous cells become tumorous. Some classical presentations include:  

 
• Sun-induced skin cancer (especially in white faced cats and white dogs)
• Nasal squamous cell carcinoma of cats
• Oral squamous cell carcinoma of cats
• Nasal squamous cell carcinoma of dogs (especially long nosed breeds)
• The nail bed squamous cell carcinoma of dogs
• The squamous cell carcinoma in situ/Bowen’s disease     

But here is also a picture of dog nasal aspergillus
 notice the depigmentation and ulceration

This page is not yet completed research

Key Points Nasal tumors are locally invasive and have a lower tendency to spread early in the course of the disease Radiation followed by surgery seems to provide the longest survial times Chemotherapy may be an option if radiation therapy is not an option

Introduction Cancer of the nasal cavity accounts for 1% of all cancers in the dog. About 80% of all nasal tumors in dogs are malignant. Nasal cavity cancer tends to be a locally invasive disease. Late in the course of the disease, the cancer can spread to other parts of the body, with the lungs being the most common site. In one study, 0 to 12% of cases were found to have metastatic disease at the time of diagnosis; however, at the time of death, 46% of the dogs had evidence of spread of the cancer to lymph nodes and lungs. The most common type of cancer that affects the nasal cavity in dogs is the carcinoma. This type of cancer includes nasal adenocarcinoma, squamous cell carcinoma and undifferentiated carcinoma and consists of 2/3's of all types of nasal tumors. Clinical signs The average age of dogs with nasal cavity cancer is 10 years and males are slightly more affected by this tumor than females. Medium to large breeds more commonly develop nasal cavity cancer than small breeds. Clinical signs of nasal cancer include bleeding from the nose, white, yellow or green nasal discharge, deformity of the face and tearing from one or both eyes. Diagnosis Although the aforementioned clinical signs can be due to intranasal cancer, other causes may include high blood pressure, fungal infection and allergies. If your pet has depigmentation of the nose and nasal discharge, fungal infection is likely to the be cause versus cancer. The first tests that are run include blood work such as a complete blood count, biochemistry profile, urinalysis and clotting profile. Chest radiographs (x-rays) are made to evaluate that patient for spread of the tumor to the lungs. Radiographs of the nasal cavity are generally of little diagnostic value to the clinician, therefore CT scan is recommended. This diagnostic modality will give the veterinarian a very good idea as to the type of disease process present (cancer vs. fungal infection) and the extent of the disease. Definitive diagnosis of a nasal tumor is based on the evaluation of a biopsy of the tumor and is typically performed at the time of a nasal CT scan. Anesthesia is required for both procedures. Treatment options No treatment is an option, however survival times following diagnosis of a malignant intranasal cancer is quite short. One study showed a median survival time of 95 days. Dogs that had bloody nasal discharge had a median survival time of 88 days versus those dogs that did not have blood in the nasal discharge had a median survival time of 224 days. Surgery alone results in median survival times that are less than six months, therefore is not recommended as the sole treatment. Surgery followed by orthovoltage radiation therapy resulted in a median survival time of 23 months in one study, however other studies have not been able to reproduce these results. The type of radiation therapy seems to play a role in patient survival. One study which included 42 dogs, showed that surgery and orthovoltage radiation therapy was inferior to megavoltage radiation therapy reported in other studies. Radiation therapy followed by surgical removal of the contents of the nasal cavity has given the longest survival times. In Adam's study (2005) of 53 dogs, the median survival time was 19.7 months with radiation alone and 47.7 months with 10 doses of 4.2 Gy per dose and subsequent surgery. Currently, this seems to be the best treatment for dogs that have intranasal tumors. Photodynamic therapy (injection of the patient with a special light sensitizer and illumination of the site with a special light) has been reported in 4 cases and resulted in clinical remission of the cancer in the patients that had epithelial tumors, but not the dog that had a sarcoma. Chemotherapy (carboplatin, adriamycin and piroxicam) has been reported in a series of 8 cases, in which 75% responded to treatment. Disease free intervals in the responding patients ranged from 150 to 510 days. This treatment may be a consideration if radiation therapy is not an option. Complications Recurrence of the tumor in most cases is expected. Chronic nasal discharge and recurrent infection in the nasal cavity is a common problem following radiation and surgery of the nasal cavity, thus intermittent treatment with antibiotics may be needed. Side effects of radiation include: loss of hair over the bridge of the nose chronic nonhealing wounds over the bridge of the nose mucositis (sores in the mouth) brain damage blindness due to cataracts or damage to the eyes oronasal fistulae - a hole that develops in the mouth that communicates with the nasal cavity Summary of prognostic factors in dogs Dogs afflicted with a nasal cavity tumor tend to have a shorter life span with bloody nasal discharge age greater than 10 years sex: males metastasis of the cancer at the time of diagnosis failure of resolution of clinical signs following radiation therapy please note that just because your dog may have one or more of these factors does not mean that treatment will not extend quality of life Specifics about cats and nasal cavity tumors Ninety-two percent of all nasal cavity tumors are malignant. Lymphoma is the most common cancer that affects the nasal cavity in cats. In a study of 123 cats afflicted with nasal cavity cancer, the second most common cancer was carcinomas (adenocarcinoma and squamous cell carcinoma). Older cats are generally affected with a median age of 9 months in one study. The most common clinical signs include nasal discharge, sneezing and vomiting. Other signs include loss of appetite, breathing difficulty and decreased activity. On study showed that lymphoma may be localized to the nasal cavity (in about one third of the cases) and radiation therapy may be the treatment of choice. Cats that are infected with Feline Leukemia Virus or Feline Immunodeficiency Virus generally do not do as well and development of lymphpoma in other parts of the body are quite possible. Almost all cases are B-cell lymphoma. Nasal lymphoma tends to be more resistant to chemotherapy than other forms of lymphoma. In a report of 19 cats that had stage 1 intranasal lymphoma, treatment with radiation and chemotherapy resulted in a disease free interval of 31 months and a median survival time of 31.4 months. Based on the fact that 17.6% of the cases had recurrences in distant locations, radiation therapy is not recommended as a sole treatment and chemotherapy should be also used. In a series of 8 cats with nonlymphomatous intranasal tumors treated with course fraction megavoltage radiation (4 to 6 treatments) the median survival time was 382 days.