Lump on Dog

"A lump on dog skin refers to an epithelial (outer skin layer) swelling. These lumps may be due to any sting or wasp bite, hematoma (accumulation of blood in a cavity), oedema (fluid in a cavity), cysts and inflammation. The most common cause of a canine skin lump is a tumor. Tumors are mostly benign in nature and non cancerous. Incurable chronic lumps with lesions should be checked to determine if it is a malignant (cancerous) form of canine skin tumor. Diagnosis usually involves clinical and physical examination, laboratory examination of the contents of the lump and a biopsy. Some lumps are only treated if they are irritating to the dog, causing pain and resulting in other conditions or problems for the affected dog. Prognosis is subject to a confirmatory diagnosis of the lump."

Causes and Forms of a Lump on Dog

Lumps may have various causes which can be initially identified during a physical examination. Several types of lumps may develop into tumors which are either benign (not cancer) or malignant (fast growing, cancerous). Most canine skin lump tumors are benign in nature.

Types of dog lumps include:

1. Hematoma: The skin surface on the ventral surface (abdomen) is hollow and has deep soft connective tissues. When blood escapes from the epithelial (outer skin layer) capillaries due to any pressure, injury or osmotic pressure (blood) gets accumulated in this hollow space, resulting in a lump on the skin surface. This lump due to hematoma feels hot when touched and gets compressed from slight pressure. Hematoma may be infiltrated by inflammatory cells and thus causes pain on palpation (when touched during examination).
   
2. Oedema: Intracellular lymphatic fluid can accumulate at the skin surface in a mass. This may happen after a sudden injury or if there is pressure on skin tissues. Oedema may appear soft, painful & usually self resolving.
   
3. Cysts: There are several cysts which may develop on superficial epithelial tissues of the skin (outer skin layer). The outer sheath of hair follicles may result in a epithelial inclusion cyst. These forms are also called sebaceous cysts and may develop in chronic cases into a benign tumor.
   
4. Inflammation: Inflammation of epithelial tissues of the skin, due to any disease, allergy or physical trauma can cause a dog skin lump. Inflammation due to flea–bites, wasp bites, parasitic infestations such as red mange, viral infections e.g. that of papilloma virus can cause inflammation and thus a lump on dog skin.  Inflammation is an immediate response of the immune system to any foreign pathogen or stress.
   
   Characteristics of typical inflammation include:
   
   
   • Pain
   • Redness
   • Loss of function
   • Warm to the touch
   • Swelling
5. Tumors: Tumors are the most common form of  skin lumps in dogs. They are either benign or malignant.  The most common form is a wart. These are usually non cancerous and harmless. The most common predilection sites for these tumors are limbs, toes and the head. These exist either due to viral factors, congenital or inherited causes, or as chronic forms of cysts. Some of examples are warts or moles, papillomas or squamous cell carcinomas.

Diagnosis of a Lump on Dog:

Lumps on a dog, which are on a superficial layer of skin can be diagnosed with a physical examination. Lumps due to an inflammatory response or oedema (pressure) appear soft and painful. Hematomas appear to be painful, and viscous (filled with a thick substance) on palpation. The content sample from a lump can be taken for further examination with a pin prick. Tumors on other hand can be palpated and can be felt as separate from deep soft tissues. A malignant form of tumor like squamous cell carcinomas may form a lump on the skin surface, contain prominent lesions and spread progressively. Epithelial inclusion cysts can be identified by a sebaceous secretion and cellular opening.

Treatment of Lump on Dog Problems:

Once the cause of a dog lump is confirmed it will be treated with the appropriate plan. Inflammations usually resolve on their own, but severe cases may require proceeding with a cooling and then compressing technique to reduce the inflammatory response. Anti-inflammatory drugs, like salicyclic acids, can be used for this purpose but should be administered only as a last option or in excessively severe cases.

Hematomas can be treated through drainage of the cavity and then with the application of a local antibiotic to reduce any secondary bacterial complications which are common in case of hematomas. Neomycin is the antibiotic used for purpose. Post drainage care and nursing should be continued for at least 2 weeks.

Benign tumors can be treated either with surgical resection or removal. Other options for treating tumors include freezing. It can be done by applying liquid nitrogen to the benign skin tumors, usually requiring a weekly application for 4 – 6 weeks.

References:

J. Morrais, Small Animal Oncology (Black well Science Ltd. 2001)

The Merck Veterinary Manual