LUMPS AND BUMPS IN THE FELINE PATIENT

Dr. Kari Mundschenk

Director, American Association of Feline Practitioners

Various lumps and bumps can occur for a variety of reasons in the cat.  They can be fluid filled as in abscesses or hematomas to solid and malignant tumors or allergic reactions.  In the case of tumors (benign or malignant cancer), it is difficult to determine without biopsy which should be of concern and which should pose no problem.  For this reason, all lumps and bumps should be evaluated by your veterinarian and if necessary, a biopsy sample will be obtained for definitive diagnosis.

Hematomas are a collection of blood underneath the skin most commonly associated with trauma.  A common area of hematoma formation is the ear.  In this case, blood vessels rupture when the cat shakes it's head and blood collects between the cartilage.  Diagnosis is by clinical history and fine needle aspiration.  Treatment involves surgical drainage of the pocket and if necessary, surgical tightening of the cartilage layers.  In some instances, scarring of the area may occur.

Abscesses are a common occurrence in cats and are usually associated with fight wounds.  In contraast to hematomas, the aspirated material is known as pus and in reality is a collection of a large number of white blood cells.  These are the cells which rush to an area to fight infection.  It is possible to get abscesses without an infection.  Treatment involves surgical opening and drainage of the pocket, the region is flushed and usually a drain is sutured in place to allow for proper wound healing.  In most instances, antibiotics are given to fight primary or secondary infection.

Allergic, inflammatory bumps occur quite frequently in cats.  Common classifications include eosinophilic granulomas, eosinophilic plaques and military dermatitis.  Also included in this category would be feline acne and mosquito bite hypersensitivity.  Causes are many including flea allergies, food sensitivities and inhaled sensitivities.  It is common to have secondary bacterial or yeast infections.  Strict parasite control is imperative and management may include diet trials, antihistamines, long term antibiotics or antifungal medications and in severe instances, corticosteroid or other immunomodulating medications.

Other true fungal infections causing lumps and bumps on cats include Cryptococcus and Coccidiomycoides.  As with most fungal infections, these usually are environmental contaminants of the soil.  Both of these infections can lead to localized or systemic infections.  They commonly occur in cats with compromised immune function either by disease, medications or age.  Diagnosis is confirmed by identifying the organism microscopically or with blood analysis or culture results.  Treatment is accomplished through the use of itraconazole, and owners can plan on at least 6 months of therapy.

Feline skin tumors occur in both benign and malignant forms.  Excisional biopsy may often be curative.  However, ALL excised tissue should be submitted for histopathologic examination as malignant skin tumors are common in cats.  The incidence of skin tumor type varies by geographical location and by country.  For the purpose of this paper, we will look at the six most common tumor types in the United States (Ogilvie, Moore).

Basal Cell Tumors:  22-26% of skin cell tumors in cats.  The benign basal cell tumor is the most common melanocytic skin tumor in cats.  They usually occur as a solitary cystic or solid dermal mass on the head or body.  Long haired cats and Siamese may be predisposed.  Surgery is usually curative.  In contrast, malignant basal cell tumors are invasive, nonpigmented tumors usually located on the head and neck.  Persian cats are predisposed.  A full work up including aspiration of regional lymph nodes is recommended.  Surgical excision, if complete, is usually curative.  If excision is incomplete, radiation therapy should be considered along with chemotherapy.

Mast Cell Tmor (MCT):  20-21% of US cats.  This type of tumor can affect cats of any age and Siamese cats are predisposed.  Usually they are solitary tumors yet can be multiple.  They are often hairless and firm, up to 5 cm in diameter.  Most MCT are found on the head and neck and need to be differentiated from eosinophilic granulomas.  Systemic involvement is rare.  If the lesion is solitary, surgical excision is usually effective yet new lesions may occur.  If multiple lesions are present, full work up including thoracic radiographs and abdominal ultrasound and special blood testing are needed to rule out systemic disease.  Adjunctive therapy may include radiation and chemotherapy.  Supportive care such as antihistamines may be needed for cutaneous reactions such as itching.  These tumors can become ulcerated and difficult to separate for eosinophilic plaques and granulomas, so it is very important to perform biopsies on all tissues to ensure proper therapy.

Fibrosarcoma/Fibroma:  16-18%.  These tumors present as firm dermal masses on any portion of the body; more common at injection sites.  Ulceration may occur on large tumors.  Diagnosis includes a thorough history, Feline leukemia test, biopsy +/- CT scan, abdominal ultrasound and lymph node cytology.  These tumors are usually locally agressive and metastasis is rare.  When it occurs, it is usually to the lungs so thoracic radiographs are also indicated.  Treatment involves wide and deep surgical excision with at least 2 cm margins.  Pre and post surgical radiation should be considered.  Chemotherapy may also be effective.  A full discussion on the role of injections to this tumor type can be had with your veterinarian.

Squamous Cell Carcinoma (SCC):  4.5-15.2% depending on geographical location.  This group of tumors are usually comprised of sunlight induced tumors in older cats.  Affected cats usually are lightly pigmented.  FIV-associated (usually due to risk factors).  These tumors appear as ulcerated lesions on the head with early lesions looking like a scratch.  Metastasis is uncommon, yet regional lymph nodes should be evaluated.  Size of tumor is predictive of outcome.  Treatment usually involves one or more of the following:  surgery, photodynamic therapy, cryotherapy, radiation therapy, and intralesional therapy.  Due to a low metastatic rate, chemotherapy is rarely performed.  Prevention of this tumor type involves keeping cats with little skin pigment out of direct sunlight during midday.  Use strategies to block ultraviolet light.

Melanoma:  0.8-2.3%.  This tumor type mostly affects older DSH cats and is more common in black and grey cats.  These tumors are usually pigmented.  They are often found on the head (pinna and ear base).  They are usually single tumors which show rapid growth and ulceration is possible.  As with mast cell tumors, mitotic index is not predictive of behavior.  These tumors commonly metastasize and are widespread so evaluation of regional lymph nodes and abdominal ultrasonography is needed.  Surgical excision is unlikely to be curative.  Radiation +/- chemotherapy may be needed.

Hemangioma/Hemangiosarcoma:  1.2-1.6%.  This tumor type affects older cats and may be more common in males.  Affected cats usually have poorly pigmented skin and sun exposure may induce formation.  Sarcomas are often ulcerated or cause bleeding under the skin.  Staging should include abdominal ultrasound and an evaluation of regional lymph nodes.  Surgical excision needs to be wide.  Due to a high metastatic rate, chemotherapy is warranted.

As noted earlier, there are other tumor types.  No matter the type of tumor, the most important item to take away is the need for wide surgical excision and histopathology.  One cannot tell a benign tumor from a malignant tumor based on visualization alone.  kdm