Cyst on Dog

" A cyst on dog by definition refers to a closed sac that has a distinct membrane and that contains air, fluid or semi solid matter. A dog cyst refers to several types of benign canine skin growths that appear on the surface of skin and is a malformations of the hair follicle. A sebaceous canine cyst is the most common type of dog skin cyst, along with other types such as a pilar cyst, matrix cyst, hybrid cyst, dermoid cyst, hygroma and keratoma. A canine skin cyst is clinically characterized by a round and firm fluctuant growth, which varies from 5 mm to 5 cm in size. A dogs history, clinical examination and biopsy are some tools used to identify the nature of the cyst. A biopsy is sometimes necessary (tissue sample for testing), since some types of cyst may be life threatening to the affected dog. Surgical removal is the treatment of choice, along with supportive therapies, which includes specific drug administration and supplementation. ."

Causes of Cyst on Dog:

A dog cyst appears to be a closed sac, covered by a distinct membrane. This membrane is formed by a division from nearby tissues. Canine cysts are mostly a malformation of the hair follicle, which lies at the base of the hair.

In most cases, the secretion of the sebaceous glands (lies at base of the hair follicle) is blocked by the superficial membranous content from nearby tissues. This blockage causes the formation of a papular or nodular and keratinized bodies over the surface of the skin, which has a distinct membrane formed due to division on the nearby tissues. This membranous body, with a distinct membrane and contents like air, fluid or semi-solid matter in it may grow to a size of 5 mm to 5 cm. This nodular and/or papular body is collectively called a cyst on dog.

There are various other pathological causes of a dog cyst. These types of dog skin cysts develop on the proximities of the legs, toes, head, vertebral column and neck. If the extremities of bones are rubbed, placed or used against hard surfaces like the ground, a chain, bedding etc, fluid gets accumulated under the surface of skin at the extremities (ends). With the passage of time, other cellular contents get mixed in it, and a semi-solid material is formed which collectively forms a dog cyst on the surface of the skin.

Types of Cyst on Dog:

There are several types of dog cysts. Classification is based upon the nature of the cyst, the pattern of its formation and the involvement of different parts of the skin tissues, particularly the hair follicles.

The following is a brief introduction to several types of cyst on dog:

• Sebaceous Cyst on Dog: This is the most common type of canine cyst, which is also called an epidermal inclusion cyst, epidermoid cyst or specifically a infundibular follicular cyst. This type of dog cyst is formed due to the dilation of the upper portion of the root sheath of the hair follicle, which blocks the flow of sebum – secretion of the sebaceous glands. This cyst varies in size from 2 mm to 5 cm in size, and the cystic formations below the cyust are 5 mm and are called milia. A sebaceous cyst on dog is partially compressible on palpation and has a small opening over the epidermis. It contains gray, yellow or brownish contents, cheesy material, which is luminal keratin.
• Pilar Cyst on Dog: This is another form of sebaceous cyst on dog, in which unlike a infundibular cyst, the lower portion of the root sheath is dilated, forming a membrane for the cyst.
• Matrix Cyst on Dog: In this type of dog skin cyst, the matrix or hair bulb is involved. The epithelium of the skin and hair bulb resembles the the root sheath of a hair follicle, thus forming a uniform matrix (hair bulb contents) over the base of hair follicle and eventually blocks the pores from which the sebaceous gland secretions are pored out.
• Hybrid Cyst on Dog: This dog skin cyst is also called a panfollicular cyst. It is the most complicated form of this dog skin condition. Different cysts on a dog, like a sebaceous cyst, pilar cyst and matrix cysts are formed on the surface of the skin. This type is mostly found in advanced cases, and causative factor is mostly idiopathic or hard to diagnose.
• Dermoid Cyst on Dog: These are congenital malformations, found on the dorsal midline of the head and vertebral column. Unlike other follicular cysts, the hair shaft is formed in the cutline of the cyst. Not all breeds of dogs are affected; certain breeds such as Terriers, Boxers, Rhodesian ridgeback dogs and Kerry Blue Terriers are more prone to dermoid dog cysts, which are formed in early embryonic life.
• Keratoma on Dog: This type of dog skin cyst is found only on the toes, formed due to severe keratinization after a traumatic injury. A protein called keratin accumulates within a sac or membrane, forming a nodular body on the surface of the skin. This cyst appears very hard on palpation and causes less or no pain at all.
• Hygroma on Dog: This is a mechanical type of canine cyst, found on the proximities of the bones. It is caused by lying on the hard ground and chains that soften the prominences and pressure points. When a dog experiences closed and idiopathic repeated injuries (unknown cause), fluids and cellular contents get accumulated in mechanically formed cavities. Hygromas are not true dog cysts, but they are included in this classification since these nodular bodies are enveloped contents over the dog skin surface.

Symptoms of Cyst on Dog:

Not all nodular and/or papular malformations on a dog are cysts; these should be differentiated clearly through clinical examination. A cyst is a sac like lump over the skin, which has distinct membrane and keratin as its primary contents along with other fluids and cellular contents.

A typical cyst on dog is represented as a bluish, yellowish or brownish nodular/papular body over the surface of the skin, which contains cheesy material in it. This cheesy material is luminal keratin mixed with cellular fluids.

A dog cyst may cause pain on palpation (when touched), and are mostly movable and causes none to severe discomfort to an affected dog.

Diagnosis of Cyst on Dog:

History of the condition, physical examination and detailed laboratory tests – such as a biopsy are some basic tools for confirmation. Cysts on dog are benign in nature and may resemble several life threatening cancerous developments. Some types of canine cysts may develop into a neoplasia or malignant cancer in advanced cases; therefore early diagnosis is essential for successful recovery.

A dog skin cyst should be differentiated from abscesses, infections, infestations, included ulcerations and fistulas by careful clinical examination, and laboratory tests.

Treatment of Cyst on Dog:

Surgical removal of a dog cyst is the treatment of choice. In most cases surgical treatment is options, since these cysts do not cause major discomfort to the dog. But, in cases where the cysts are the cause of any disturbance in the dogsphysiology, such as spreading over time or diagnosed as potential cancerous developments; cysts should be removed surgically.

Surgical treatment is always recommended by a veterinarian, because affected dogs may rub, scratch or chew the nodular cysts, which may cause a severe secondary infection and due to the increased chance of ulceration and abscess formation. These complications due to injury may cause severe trouble for the dogs health.

Along with surgical treatment, supportive medical and alternative approaches are highly recommended. A quality shampoo with the capability to remove excessive oiliness and scaling over the skin should be used according to the recommendations of a veterinarian, and specific drugs as such as anti-inflammatory drugs and skin health supplements (preferably natural remedies such as Skin and Coat Tonic) should be used.

References:

Paterson, S. Skin Diseases of the Dog (Blackwell Science - 1998)

The Merck Veterinary Manual