What is that bump? - Cutaneous mast cell tumors in cats

Just like any cat that comes through our front doors, Mr. A and Mr. B get wellness exams periodically. On February 7, one of our technician discovered a small, raised bump on Mr. B's hock.

Since new bumps on a cat should be looked at to ensure that they are not cancerous, we had Dr. Demos give Mr. B a thorough exam and take a sample from the mass with a needle. This is called a Fine Needle Aspirate (FNA), and can often give us a good preliminary idea of the kind of lump we are dealing with.

Once we had a sample of the mass, the images we saw under the microscope showed this:

 Very dark-staining cells filled with small granules and lots of small granules in the background. These are mast cells.

Mast cells

 Mast cells can easily be compared to other abnormal cells, like these white blood cells, called lymphocytes, that are abnormal due to the presence of a cancer called lymphoma.

Lymphoma

 Since we were suspicious of a mast cell tumor, we scheduled Mr. B for surgery to remove the mass. He fasted prior to surgery, and then was given preliminary pain medications. We anesthetized him and shaved and scrubbed the surgical site. Even though the lump was quite small, the surgery was very delicate, because the hock is an area with prominent blood vessels and tendons, and has very little fat.

Once the mass was removed, we placed it in formalin to send to a pathologist for analysis. Even though we have a good idea what the mass is before we remove it, we like to confirm it with the experts, and also have the mass checked to ensure that we removed all of it. This is done by measuring the "margins" around the edge of the abnormal tissue.

"Clean margins" (a ring of completely normal tissue around the mass) mean that the mass is less likely to recur. If the margin of normal tissue around the mass is too small, there increased risk of the mass re-occurring. The need to have clean margins around the mass is also the reason that you may notice the area where a mass was removed is often quite a bit larger than the mass was, originally. In some areas, such as the leg, face and tail or the top of the head, where there is not a lot of extra skin, it may be very difficult to create good margins for a mass without risking the integrity of other parts of the body. This is why it is a good

After surgery, we placed Mr. B in a cage, to ensure that he was fully recovered before we let him run around. Usually recovery from a short surgical procedure like a skin mass removal takes just a few minutes from the time that the anesthetic gas is turned off. In Mr. B's case, he was sitting up and asking for post-surgical treats within about 10 minutes.

First, Mr. B fasted for his surgery. He was not very excited about that.

Next, we set up for surgery.

We placed Mr. B under anesthesia, intubated him and shaved and prepped his surgical site.

Post-surgery, we cleaned the sutured incision site, and let Mr. B recover on his warm water blanket.

Mr. B completed his recovery in a cage, and then enjoyed a post-surgical meal. His eyes are very dilated from the pain medication we used. It made him VERY happy.

What is a Mast Cell? Mast cells are a normal cell type found in the body that is involved in various functions including the immune system, wound healing, allergies and inflammation. The granules that they contain are really little sacs that carry important chemicals such as heparin, histamines and antimicrobial chemicals.They are developed in the bone marrow and disperse throughout the body to the skin, connective tissues and the lining of the abdominal organs such as the stomach and intestines.

Despite their beneficial activities in the body, sometimes, mast cells go bad. Mast cells play a big role in anaphylactic reactions (the kind of serious allergic reaction many people experience due to bee stings). Also, in addition to forming mast cell tumors, they can also be involved in autoimmune diseases. In humans, mast cells have been implicated in rheumatoid arthritis.


About 20% of all skin tumors in cats are mast cell tumors, and these types of tumors occur less frequently in cats than in dogs. About 90% of cutaneous mast cell tumors in cats are benign, and excision (surgical removal) is the cure. Mast cell tumors in the internal organs are a different matter.

Once we had sent in Mr. B's mass for biopsy, we received the following report from the pathologist a few days later:

Microscopic Description	Small left hock skin mass contains a dermal solid proliferation of minimally pleomorphic small neoplastic mast cells. Mast cells efface adnexal structures. One mitotic figure per 10 high power fields is seen. Tumor free margins measure approximately 1 mm.
Microscopic Interpretation (Biopsy)	Cutaneous mast cell tumor
Comments:	Histologic features of this skin tumor are consistent with a benign dermal mast cell tumor. Cutaneous mast cell disease accounts for approximately 21% of all feline skin tumors. Grading scheme similar to canine mast cell tumors has not been developed for feline neoplasms. Mitotic count (over 5/10 HPF) is the only criteria that has prognostic significance in determining benign from malignant (Vet. Pathol 2010; 47(4); 643-653). Neoplasms with high mitotic rate may have concomitant increase in mast cell pleomorphism.

Now we can be confident that the tumor was removed entirely, and that it was benign.

Mr. B is now strutting his stuff as usual, with lots of commentary on his healing progress. In 10-14 days, he can have his sutures out and in 6-8 weeks, his hair will have regrown, and no one will even see his scar!

We wonder whether Mr. B is asking for a matching shaved spot on his other legs.

Chronic Nasal Discharge in Cats

CHRONIC NASAL DISCHARGE

What is meant by the term "Chronic Nasal Discharge"?

When a cat has a discharge from its nose that lasts more than 2 months, it is considered chronic.  The discharge may be thin and clear like water (serous), thick and yellow or green like pus (purulent), bloody (sanguinous or hemorrhagic), or a combination. Clear fluid or mucousy discharge may be an indication of irritation or viral infection. Thick, yellow fluid or pus may be a sign of a bacterial infection. Reddish fluid can be a sign of intense or chronic irritation, destruction of the nasal mucous membranes or bones (turbinates). Trauma can also cause a bloody nasal discharge.

Foreign bodies only affect one nostril. Fungal infections and tumors may affect one or both nostrils, while viral infections most often affect both, though one side may be worse than the other.

What causes a chronic nasal discharge?

A view into the nasal canal and the papery turbinate bones

Chronic nasal discharge is not a diagnosis; rather, it is a term that describes the signs of disease in the nose and frontal sinuses.  Almost all disease conditions that occur in the nose will cause irritation and inflammation to the lacy bones in the nose, called turbinates.  The presence of disease in the nose is called rhinitis.  The turbinate bones are easily distorted and destroyed.  When that happens, bacteria that normally live in the nose grow rapidly, causing a secondary bacterial infection.

The frontal sinuses are hollow cavities in the skull and are located just above the eyes.  They are connected to the nasal cavity by a small canal.  Most diseases that occur in the nasal cavity have the ability to move through these canals into the frontal sinuses.  When the sinuses become involved and develop inflammation, this is called sinusitis.

Chronic nasal discharge may result from several disorders involving the sinuses and nasal cavity.  These include:

                Chronic viral infection

                Chronic bacterial infection

                Chronic fungal infection

                Dental disease

                Nasal foreign body (e.g. grass seed)

                Nasal tumor

                Inflammatory polyp

                Parasite infection

What tests should be done to make an accurate diagnosis?

There are several diagnostic tests that should be done for a cat with a chronic nasal discharge.  A blood profile will often detect underlying diseases that can contribute to a nasal disease.  Testing for the feline leukemia virus (FeLV) and the feline immunodeficiency virus (FIV) is important because these viruses have the ability to suppress the cat's immune system, making recovery from normally mild infections difficult (or even impossible). 

Nasal x-ray. One side of the nose has poor detail which suggests that the delicate bones of the nasal passages, the turbinate bones, are being destroyed.

It is very important to make radiographs (x-rays) of the skull.  Special positions are necessary to view the nasal cavity and frontal sinuses.  These require sedation or a short-acting anesthetic.  A nasal flush is a diagnostic procedure used to collect material from deep within the nasal cavity.  This material can be studied under the microscope (cytology) and can also be cultured.  Although it is not particularly traumatic to the cat, anesthesia is required, so this procedure is usually done in conjunction with radiographs.  This allows more than one procedure to be done while the cat is under anesthesia.

Anesthesia allows close inspection of the throat, the area above the soft palate, and the nasal canals. This cat had a large buildup of extremely thick mucus above the soft palate.

Some veterinarians have a specialized instrument called an endoscope which allows the veterinarian to actually look inside the nose, as well as to examine the back of the throat and the area around the soft palate.  In order to pass this small flexible tube into the area of interest, anesthesia is required.

There are some diseases that can only be diagnosed with a biopsy of material deep within the nasal cavity.  A biopsy requires recovery of an actual piece of tissue, so surgery is often required for this procedure.

Fungal organisms and a plaque of fungal growth inside the nose of a cat 

Foreign objects within the nasal passage can sometimes be detected with radiographs.  If a foreign body is suspected but not visualized, endoscopy may be helpful, depending on where the foreign body is located.  For some cases, exploratory surgery of the nasal cavity is needed.

As you can see, it may require several days or weeks of testing to determine the cause of a chronic nasal discharge.  When the diagnosis remains elusive, more sophisticated tests may be required.  Veterinarians unable to perform these tests often refer the cat to a specialist.

How is a chronic viral infection treated?

Respiratory viruses, which can infect the nose, may persist and lead to long term viral rhinitis/sinusitis.  No drugs are available to kill these viruses so this type of infection is often incurable but many cats respond to antiviral medications such as Famciclovir.

How is a chronic bacterial infection treated?

Administration of antibiotics alone is usually unsuccessful in curing bacterial infections of the nose and sinuses because the bacteria have become entrapped within the turbinates, and reinfections are frequent.  Although many cats improve while taking antibiotics, cortisone, or antihistamines, they may relapse when these drugs are discontinued.  The use of drugs that stimulate the immune system and the surgical removal of the turbinates have been successful in some cats.  However, others do not respond well.  Overall, the prognosis is guarded.

How is a chronic fungal infection treated?

The most common fungal infection in the nose is caused by Cryptococcus neoformans. Because some of the drugs used to treat this organism are quite expensive and will occasionally cause adverse effects, they are not used unless a firm diagnosis is made.  Fortunately, the newer antifungal drugs have fewer significant side effects and many cats with fungal diseases can be successfully treated.  If the cat is infected with the feline leukemia virus or feline immunodeficiency virus, the outcome will usually be less favorable.

The image below shows a cat named Parker who came to us with a severe swelling in her nose. Microscopic evaluation of samples collected from her nose showed the fungal organism Cryptococcus. Treatment was started and over time, her nose returned to normal.

How is dental disease treated? 

A cat's tooth roots are located very close to the sinus cavity, and if the tooth becomes infected, pus or fluid may drain from the nose. If the infected tooth becomes a severe enough problem, the cat may have facial swelling or swelling of the eye, the tongue may stick out, or the tooth may completely fall out, leaving an opening straight into the sinus cavity.

Disease of this type is treated with a thorough dental cleaning and extraction of the infected teeth, followed by a course of antibiotics. If the disease is bad enough, the cat may be prescribed antibiotics prior to dental care, too.

Read more about what is involved in feline dental care.

How is a nasal foreign body treated?

Nasal mites

When a piece of grass, a seed, parasites or other foreign material lodges in the nasal cavity, the membrane which lines the nose produces large amounts of mucus in response to the irritation.  In addition, affected cats will sneeze violently in an attempt to expel the foreign body. 

If the foreign body cannot be sneezed out, the veterinarian must take steps to remove it.  When a nasal foreign body is suspected but cannot be seen on radiographs or with an endoscope, exploratory surgery may be needed.  If it is found and removed, the prognosis is good.

The following video shows the removal of a Cuterebra larva that was lodged in a cat's nose. He had chronic nasal discharge and excessive sneezing that was not improved with antibiotic treatment. After the Cuterebra was removed, his nasal discharge went away and he stopped sneezing.

How is a tumor treated?

Most nasal tumors are malignant.  Complete surgical removal is very unlikely, so chemotherapy or radiation therapy must be considered.  Unfortunately, many nasal tumors do not respond to either treatment, so the prognosis is poor.  However, when surgery is performed to get tissue for biopsy, most surgeons remove as much of the tumor as possible.  Following this procedure, the cat may be greatly relieved of the nasal discharge and remain improved for several months.  However, in almost all cases, the tumor can be expected to recur. In some cases, however, chemotherapy and/or radiation treatment are successful and the cat will go into remission for as long as several years. It is notable that after a cat has been treated with radiation, the hair at the site of the treatment will likely change color.

This 12 year old cat has been having chronic nasal discharge and sneezing for 2 weeks. He has significant dental disease, but another likelihood at his age is that he may have a tumor. Dr. Brooks' plan for him is to extract his infected teeth and perform a surgical biopsy to determine the extent of his problem.

Several of this cat's teeth have already fallen out and another is almost ready to.

How is an inflammatory polyp treated?

Inflammatory polyps are non-cancerous masses of tissue that are composed of inflammatory cells. Surgery is often successful in removing much of the polyp, but there is a high probability of regrowth if all of the polyp cannot be removed.  Since polyps often begin in the internal ear and grow down the Eustachian tube into the back of the nose, their removal can require extensive surgery that may not be completely successful.  The prognosis for an inflammatory polyp is guarded because the entire polyp cannot be removed in some cases, however, if the entire polyp is successfully removed, the cat will completely recover.

The cat below had an extremely large nasopharyngeal polyp. Once it was removed, her sneezing and nasal discharge resolved completely!

Any time that your cat has discharge from the nose, it is a good idea to have the cat examined by a veterinarian, because the potential causes of chronic nasal discharge are extremely varied, and treatment for chronic nasal discharge is highly dependent on the cause.