Nasal adenocarcinoma is a slow, progressive local infiltration of tumor cells from the tissues that line the inside of the nose. Most nasal adenocarcinomas initially originate unilaterally (affecting one side of the nasal sinuses) and then extend to both sides.
Adenocarcinoma is the most common cause of nasal cancer in dogs. The cause of nasal adenocarcinoma is unknown. It has been suggested that chronic exposure to environmental pollutants may be a contributing factor in dogs that spend a lot of time in urban environments. Exposure to passive smoke, wood dust and / or toxins from industrial plants has been weakly related to nasal tumors.
Almost certainly, genetics play a role. Dogs with nasal adenocarcinoma usually have nasal secretions containing mucus, pus and / or blood. They often develop protuberances on the muzzle, protrusion of one or both eyes, excessive tearing, sneezing, bad breath and spontaneous nosebleeds (nasal bleeding).
In addition to the tissues present in the nasal cavities, adenocarcinomas can affect a number of glandular organs in domestic dogs, including salivary glands, thyroid glands, lungs, pancreas, kidneys, skin (sweat glands, sebaceous glands), stomach, small and large intestine, rectum, anal sacs and prostate gland.
Despite intense research, medical science has not yet discovered the precise causes of the various forms of adenocarcinoma, including locally invasive and usually metastatic nasal adenocarcinoma. It has been suggested that thechronic exposure to environmental pollutants may be a possible contributing factor in dogs who spend most of their time in urban environments. Exposure to passive cigarette smoke, wood dust and / or toxins from industrial plants has been weakly related to nasal tumors in domestic dogs.
In a more general sense, almost all cancers are “caused” by accelerated and uncontrolled cellular reproduction and tissue growth. As a rule, most body cells have a predetermined lifespan and, when they die, are replaced in an orderly and controlled manner by the dog’s genes. When something disturbs this normal genetic process, cell mutations can arise. These mutated cells tend to reproduce at an extremely fast rate, without the normal control action mentioned above. They can gather in masses, called tumors, capable of overwhelming normal cells and compromising normal bodily functions.
Furthermore, cancer cells are no longer able to perform the same functions as normal cells before the mutation. In view of their totally uncontrolled reproduction, it follows that even the new cells will be characterized by the same inability to perform normal cellular functions. Cancer cells can enter the dog’s bloodstream and / or lymphatic circulatory system and migrate to remote locations, a process known as metastasis. They can settle almost anywhere in the body and continue to reproduce uncontrollably, progressively damaging and destroying tissues.
In addition to the dog’s genetic makeup and possible genetic mutations, there are environmental carcinogens potentially capable of increasing the risk of cancer in pets. Carcinogenic substances can be ingested, inhaled or acquired through physical contact and cause a possible alteration in the genetic code of the dog, compromising the normal control and balance system that regulates the function, growth, reproduction and cell death in an orderly manner.
The symptoms of canine adenocarcinoma vary according to the glandular tissue involved, the severity and extent of infiltration and metastasis and the general systemic health of the dog, in particular the functional strength of the immune system. Nasal adenocarcinoma tends to manifest a fairly constant set of clinical signs, including:
- Nasal secretion – one-sided and / or bilateral (which comes out of one or both nostrils), mucus and / or pus (mucopurulent nasal secretion), bright red blood (nasal hemorrhagic secretion), watery nasal secretion (serous)
- Nose bleeding (epistaxis) – intermittent and progressive, unilateral and / or bilateral (which protrudes from one or both nostrils)
- Excessive tearing (continuous secretion of tears, epiphora)
- Ocular malposition (abnormal protrusion or protrusion of the eyes, exophthalmos)
- Sneezing and / or “reverse sneezing” (literally reverse sneezing)
- Seizure crisis (in case of metastasis to brain tissue)
- Facial deformities (masses taking up space, bone changes)
- Deformation of the hard palate
- Deformation of the upper jaw
- Pain (especially when examining the nasal sinuses or when the mouth is open)
- Obstruction of the nasal passages (blocked nostrils)
- Breathing difficulty (dyspnoea) through one or both nostrils (physical obstruction of the air flow)
- Enlarged lymph nodes (especially mandibular lymph nodes)
In dogs with nasal adenocarcinoma, the results of blood tests (complete blood count and biochemical serum panel) and urine in general are normal. Most vets will pick up gods nasal secretion samples by swab and will submit them to a diagnostic laboratory for evaluation, including microscopic evaluation of the cells present in the samples (a process known as cytology) and possibly by bacterial culture and sensitivity. If the dog has a history of spontaneous nosebleeds of unknown origin, the vet will likely also conduct a coagulation profile to check for the presence of primary disorders in the dog’s ability to form normal blood clots. This will likely include a test related to the bleeding time of the buccal mucosa (or Bleeding Time).
More advanced tests include cranial radiographs for the search for asymmetrical destruction of the nasal bones (nasal turbinate), facial bones and / or soft tissue masses. The thoracic radiographs they can be recommended for lung metastasis. Much more advanced diagnostic methods include computed tomography (CT) and / or magnetic resonance imaging (MRI), each of which provides a more sensitive assessment of the extent of abnormal tissue. A procedure called can be performed rhinoscopy to view the lining of the nasal sinuses and to allow the veterinarian to take tissue biopsies of any fleshy masses or other tissues that appear to be abnormal. This can be a difficult process, especially in the presence of large quantities of blood or other nasal secretions. The biopsy specimens will be sent to a diagnostic laboratory to definitively determine the presence or absence of adenocarcinoma. The aspiration of regional lymph nodes, in particular of the mandibular lymph nodes, can reveal the presence and spread of primary nasal adenocarcinoma.
There is no diagnostic protocol for nasal adenocarcinoma. The vet will adopt an appropriate diagnostic plan based on the dog’s condition at the time of the visit.
Nasal adenocarcinoma can be difficult to treat. In many cases, it can be managed, although complete healing is rarely possible. Therapeutic goals include alleviating discomfort, preventing further metastasis, eliminating as much cancerous tissue as possible and prolonging a good quality of life for the dog.
If the dog experiences uncontrollable recurrent nosebleeds, immediate medical treatment may include sedation, tamponade with gauze soaked in special drugs and application of cold compresses on the nose and muzzle. If the presence of a secondary bacterial infection is confirmed, the use of antibiotics and steroidal or non-steroidal anti-inflammatory drugs may be recommended.
L’surgery it is the elective treatment for many canine malignancies. However, surgery alone is rarely effective in treating nasal adenocarcinoma, since it is virtually impossible to surgically resect all the abnormal tissue present in the small limited spaces of the nasal cavities. Of course, much of the localized tissue involved, including the turbinates or other facial bones and the tissues that line them, can be surgically removed, both before and after radiation therapy, depending on the location and severity of the cancerous infiltration.
Biopsy specimens collected by surgical removal will be sent to a diagnostic laboratory, where experienced veterinary pathologists will examine them to determine the exact type of tumor and the presence of appropriate surgical margins. When a focal cancerous mass is removed, the surgeon attempts to remove even a small amount of normal tissue around the entire mass of abnormal tissue in order to obtain what are called “unimpaired surgical margins”. In the event that it is possible to continuously observe normal (non-cancerous) tissue around all the edges of the removed cancerous mass microscopically, the animal has a very low risk of metastasis from that tumor site. Unfortunately, this is usually not possible in cases of nasal adenocarcinoma.
To treat nasal tumors, the can be used radiotherapy, both internal (brachytherapy) and / or external (teletherapy). This type of therapy is designed to kill malignant cancer cells in a defined physical area by exposing them to high levels of lethal radiation. These procedures are typically performed on a daily basis for several weeks or more and should therefore be performed on an inpatient basis. Radiation therapy treatments are usually well tolerated by most dogs and can prolong their survival and improve their quality of life.
For dogs with nasal adenocarcinoma, another option may be the chemotherapy (treatment with intravenous or oral medications). Chemotherapy kills cancer cells differently. It is unable to affect a specific physical area of cancer cells, but passes through the circulation to affect all rapidly dividing cells present in the body. In view of this mechanism of action, chemotherapy is not as effective as radiation therapy in case of nasal adenocarcinoma. Chemotherapy has been reported to alleviate the symptoms of nasal tumors for a few months, but cannot cure the condition or increase overall survival time.
In some cases, veterinarians may recommend one combination of therapies, as surgery associated with radiation therapy and / or chemotherapy. One of the adverse effects of both radiation therapy and chemotherapy is the damage or destruction of many normal cells. Other existing and emerging treatment options for animals with neoplasia include molecular target therapy, immunotherapy, hyperthermia, cryotherapy, phototherapy, photochemotherapy, thermochemotherapy and other unconventional or emerging alternative therapies. Most of these new approaches are not yet widely available in veterinary medicine.
The goal of treatment is obviously to eliminate only malignant cells. Unfortunately, it is currently not possible to completely isolate healthy tissue from cancerous tissue during these surgical, radiotherapy or chemotherapy treatments. Following these treatments, the onset of side effects is possible, including nausea, vomiting, diarrhea, weakness, lethargy, lack of appetite and weight loss.
The prognosis for dogs affected by any form of cancer is highly variable, depending on the type of neoplasm involved, the location and nature of the tumor, the possible metastasis, the staging at the time of diagnosis, the owner’s motivation and body condition, appetite, activity level and general health of the dog.
Thanks to timely diagnosis and aggressive therapy, some dogs with nasal adenocarcinoma can be well managed and live happily for months or even years.
Since the cause of nasal adenocarcinoma has not been understood, it is virtually impossible to describe a significant prevention protocol.
Early diagnosis almost always improves the prognosis of a dog with cancer. When the owner notices a bump on the dog’s muzzle, an abnormal protrusion of one or both eyes or spontaneous nosebleeds for no apparent reason, a visit to the vet is recommended for a thorough check. Thanks to timely diagnosis, aggressive treatment and constant management, dogs with nasal adenocarcinoma can continue to live for months or years.