Nasal tumours in dogs: symptoms and treatment

Overview

What types of tumour occur in the nose?

Tumours of the nasal cavity and sinuses account for about 1–2% of all canine tumours. More than 80% of nasal and sinus tumours are malignant. The most common group is carcinoma, arising from cells lining surfaces or glands. The most common carcinoma is adenocarcinoma, which arises from glandular epithelium. Sarcomas originating in connective tissue can also occur in the nasal cavity. Lymphoma, a cancer of lymphocytes, is a less common possibility. Rare mast cell tumours can also occur in the nasal cavity. In a study of one nasal carcinoma type, all 16 dogs had a tumour involving at least the back of the nasal cavity. These tumours often spread first into neighbouring structures and metastasise relatively late.

Causes

A tumour can originate in the epithelium lining the nasal cavity. Epithelial tumours account for an estimated 50–75% of canine nasal cavity tumours. About 2/3 of nasal tumours are carcinomas and about 1/3 are sarcomas. The environmental factors contributing to an individual dog's tumour usually cannot be established with certainty.

A rare nasal hamartoma, a developmental tissue abnormality, can resemble a tumour and cause bloody discharge. Fungal infection of the nose and sinuses can cause muzzle pain and nosebleeds. Sudden sneezing may be associated with a plant awn entering the nose. Other possible causes of bloody nasal discharge include injury and clotting disorders. A tooth root abscess can cause nasal signs if infection extends towards the nasal cavity.

Risk factors

Nasal cavity and sinus tumours are typically diagnosed in older dogs. Across studies, dogs had an average age of 8.7–10.7 years at diagnosis. Long- and medium-muzzled breeds appear more susceptible to nasal tumours than short-muzzled breeds.

A tobacco smoke study compared 103 dogs with nasal tumours with 378 dogs with other cancers. Across the whole group, smoke-exposed dogs had an odds ratio of 1.1 for nasal tumours compared with unexposed dogs. In the long-muzzled subgroup, living with someone who smoked was associated with an odds ratio of 2.0. Another study found no association between tobacco smoke and nasal tumours. That owner questionnaire study received responses from owners of 129 dogs with nasal tumours and 176 comparison dogs. Indoor coal heater use was associated with an adjusted odds ratio of 4.2. Indoor paraffin heater use was associated with an odds ratio of 2.2 in the same study.

Typical symptoms

Discharge often begins in one nostril and may later affect both.

• Nasal discharge may contain mucus, pus or blood.
• Your dog may sneeze repeatedly.
• Nosebleeds may occur intermittently.
• Breathing may sound noisy or airflow through the nose may decrease.
• The muzzle may swell or one side of the face may change shape.
• One eye may water more than usual.

In a study of one nasal carcinoma type, 12 of 16 dogs had nosebleeds (75%). Abnormal breathing sounds were noted in 6 of 16 dogs in the same study (38%). The duration of symptoms before presentation was available for 9 dogs and ranged from 7 to 270 days. Reduced airflow was more often associated with a nasal mass than with fungal rhinitis.

Complications and consequences

Growth near the eyes and brain

A nasal tumour can destroy the nose's bony supporting structures and alter facial shape. If it extends behind the eye, the eye may protrude further than normal. This can predispose the cornea to inflammation if the eyelids no longer cover the surface normally. An obstructed tear duct can cause watering of the eye. In the study of one nasal carcinoma type, the tumour had extended into the eye socket in 11 of 16 dogs (69%). It extended into the oral cavity in 7 of the 16 dogs (44%). Growth into the skull can cause signs such as confusion, visual disturbances or seizures.

Metastases may develop in sites such as regional lymph nodes or the lungs. At diagnosis, regional lymph node metastases have been found in about 6% of dogs with nasal tumours.

Diagnosis at the vet

Imaging and tissue sampling

Your vet examines muzzle shape, airflow through the nostrils and any eye signs. If nasal bleeding is heavy, blood tests can assess platelet numbers and clotting. A CT scan of the head shows the tumour's location and extent. CT images can reveal loss of nasal bone structures. Imaging is usually performed before biopsy because sampling can cause bleeding that makes images harder to interpret. Endoscopy allows your vet to see inside the nasal cavity and sample a visible lesion directly. Microscopic examination of the tissue sample establishes the tumour's cell type.

The initial CT scan and tissue sample were inconclusive in 2 dogs with transitional carcinoma. Their tumours were confirmed only after repeat imaging and another tissue sample.

A small comparison study included 22 animals, 17 dogs and 5 cats, all diagnosed with nasal tumours. A tumour was the leading suspicion on CT in 11 of 12 examinations (91.7%). On endoscopy, it was the leading suspicion in 9 of 14 examinations (64.3%). Only 4 animals in the study underwent both procedures. The difference in this small comparison was not statistically significant.

Assessing the extent of spread

In the modified Adams staging system, stage 1 means a tumour confined to one side of the nasal region without bone damage beyond the turbinates. Stage 2 involves other bone but not the eye socket or tissues beneath the skin or mucosa. At stage 3, the tumour extends into areas such as the eye socket or nasopharynx. At stage 4, it involves the cribriform plate or brain. MRI may help assess soft tissue changes extending inside the skull more precisely. In the nasal transitional carcinoma study, CT showed cribriform plate bone loss in 12 of 16 dogs (75%). However, findings suggesting growth into brain tissue appeared in only 2 dogs (13%). Brain tissue changes were not confirmed by tissue samples. Chest imaging can look for lung metastases. A fine-needle sample can be taken from a regional lymph node to assess spread.

Treatment

Radiotherapy and other options

Your vet chooses treatment according to the tumour type and extent of spread. Radiotherapy is the first-line treatment for nasal adenocarcinoma. Complete surgical removal is often difficult because the tumour grows close to the eyes, brain and other important structures. CT images are used to plan radiotherapy so that radiation can target the tumour while sparing surrounding tissues. For treatment, your dog is positioned as they were for the planning scan. Dogs are usually under general anaesthesia during external beam radiotherapy to keep them still while radiation is delivered. Palliative radiotherapy aims to relieve pain and other symptoms caused by the tumour. Chemotherapy may be considered for some tumour types. Your dog's general condition and blood results are monitored during chemotherapy.

Treatment outcomes and outlook

Among 139 carcinoma patients receiving no tumour-directed treatment or no treatment at all, median survival from diagnosis was 95 days. The 107 dogs with nosebleeds in that study had a median survival of 88 days. For the 32 dogs without bleeding, it was 224 days.

In a palliative radiotherapy study, median survival in the first group of 17 dogs was 298 days. In 24 dogs receiving a different radiotherapy protocol, median survival was 375 days. In this radiotherapy study, nosebleeds did not appear to affect survival once the extent of tumour spread was taken into account. In a study of precisely targeted stereotactic radiotherapy, 175 dogs received one treatment course. Their median survival was 441 days.

In another radiotherapy study, dogs with cribriform plate damage had a median survival of 179 days. Dogs in the same study whose cribriform plate remained intact had a median survival of 306 days. Dogs with lymph node metastases had a median survival of 126 days. Without identified lymph node metastases, median survival was 226 days.

Radiotherapy can irritate skin and the oral lining within the treatment area. Early adverse effects usually heal within 4–6 weeks after treatment ends unless severe. Later effects may include dry eye if the eye was within the treatment field. During stereotactic treatment follow-up, 13 of 182 dogs developed a fistula connecting the nasal cavity to the mouth or skin (7.1%). Fistulas appeared 83–1,733 days after stereotactic treatment. The median time was 425 days.

Prevention

The association between passive smoking and nasal tumours in long-muzzled dogs concerned a subgroup, and study results on canine nasal tumour risk are conflicting. A smoke-free home prevents exposure to tobacco smoke produced indoors. Tobacco smoke residues can also accumulate on clothing, furniture and your dog's coat. Dogs can also inhale tobacco smoke compounds from household dust. Smoke residues may enter a dog's mouth when they lick a smoker's skin or clothing. A tumour diagnosed early generally has a better outlook than one already invading surrounding structures.

Important for dog owners

Note when nasal discharge started, which nostril it comes from and whether it has become bloody. Tell your vet if breathing has become noisier or one eye has started watering. Treatment response is also assessed by whether airflow through the nose improves. Symptoms returning after treatment may be associated with tumour progression. After stereotactic radiotherapy, persistent rhinitis was suspected in 54 of 88 dogs with relevant follow-up information (61%). Persistent inflammation may cause mucus or pus in the discharge. Keep a record of whether discharge is constant or intermittent and whether your dog can rest without breathing difficulties.

Frequently asked questions

Could persistent nasal discharge be caused by an infection?

A nasal fungal infection can cause discharge and pain similar to a tumour. Aspergillosis can often be identified by fungal culture if the sample comes directly from a fungal plaque. If imaging shows a nasal mass, a tissue sample helps establish what it consists of.

Why is a biopsy needed if the tumour is visible on CT?

CT shows where the mass is and the direction in which it has spread. Tumours that look similar on images can have different cell types. Microscopic examination of tissue determines the tumour type, which guides treatment selection alongside the extent of spread.

Why are nasal tumours not usually removed surgically?

A nasal cavity tumour may invade bone and surrounding tissues. A lesion growing close to important structures is difficult to remove completely. Radiotherapy can also target areas from which the tumour cannot safely be removed.

What is palliative radiotherapy intended to achieve?

Palliative radiotherapy aims to relieve tumour-related pain and other symptoms. In some cases, it can also slow tumour growth. Response may be assessed by improvements in nasal airflow and reductions in discharge, for example.

Does new nasal discharge after treatment mean the tumour has returned?

Discharge returning can indicate tumour progression. Persistent rhinitis can also occur after radiotherapy, causing sneezing as well as discharge. When symptoms change, your vet may investigate with repeat imaging and compare the findings with previous images.