eChapters

Benign/malignant tumor may arise from fibrous tissue. Fibroma mostly occurs in the dermis or subcutis of limbs and head.

Perianal gland tumors originate around the anus of the dog, upper and lower part of the tail and prepucial area. Retention of gonadal hormone receptors is one of the causes for perianal gland adenoma and adenocarcinoma.Cytology reveals the presence of hepatoid cells with centrally placed nuclei and prominent nucleoli. A small flattened reserve cells or resting cells are also noticed around the hepatoid cells. In malignant variety, the cells containing large vesicular nuclei, eosinophilic granular cytoplasm and binucleated cells, mitotic figures, reserve cells, moderate stroma and lymphoplasmacytic infiltration are seen (Figure 55 & 56).

The tumor arising out of ceruminous gland might develop subsequent to chronic otitis externa in dogs. It may be a benign or malignant tumor of ceruminous gland epithelium. It is more common in the external ear canal of dogs.

It is one of the common epithelial skin tumors. It is more common in head but also recorded in other sites such as back, tail, limb, trunk and eyelids. It is a tumor of sebaceous cells. In sebaceous gland adenoma, it has predominantly sebocytes with less of basaloid reserve cells while in sebaceous epithelioma variant, more of basaloid reserve cells are seen with less of sebocytes.

This is a benign/malignant tumor originating from the apocrine and eccrine sweat glands in dogs. It is usually recorded in the head and neck region but it may occur on any site.

Cytology reveals clusters of moderate to severe exfoliated neoplastic cells which contain round nuclei slightly eccentric in position in the light pale granular cytoplasm. In carcinomas, clusters of basophilic epithelial cells had large nuclei and prominent nucleoli. It may also contain one or two large secretory droplets.

This tumour may occur due to specific mutation in the p53 tumor suppressor gene. This is one of the most common epithelial tumor of dog. It is classified into well differentiated, moderately differentiated and poorly differentiated tumour.

Etiology

It is a pruritic transmissible dermatological condition caused by Cheyletiella yasguri, one of the surface living mite.

Etiology

It is an uncommon endocrine related skin disorder. It is very rarely encountered in neutered dogs.It is always associated with cryptorchidism and sertoli cell tumor. This condition is closely accompanied with endocrine related testicular tumor followed by skin lesion and feminization.

A very common condition caused by Malassezia pachydermatis in dogs. It is also caused by predisposing allergic skin disease. It occurs in ventral neck, ventral abdomen, axilla, face, pinnae, feet and forelegs. Tape impression smear will reveal numerous yeasts.

Etiology

It is a relatively rare skin disease or dermatologic condition. Hypersensitivity reaction is one of the suggestive cause for this condition characterized by nodules or plaques which are seen in the skin, oral mucosa and external ear canal.

Etiology

It is a rare idiopathic primary dermatitis condition seen mainly in Daschund.

A) Hypothyroidism

Etiology

It is one of the common endocrine disorders of skin of dogs mainly due to deficiency of thyroid hormone followed by cutaneous and non cutaneous signs. It is caused by lymphocytic thyroiditis or idiopathic thyroid necrosis and atrophy. Deficiency of thyroid hormone hinders the metabolic processes throughout the body.

Etiology

Canine dermatophytosis (canine ring worm) is a relatively common dermatological condition caused by Microsporum canis, Trichophyton mentagrophytes and Microsporum gypseum. These fungi are keratinophilic in nature. It can occur mostly in the face and forelegs.

Scales are having imperfectly keratinized superficial layers of the epidermis characterized by cracks or thin flakes.

Crust is characterized by the presence of desquamated squamous epithelial cells. The dried exudate consists of necrotic cell debris, leucocytes, RBC’s, plasma proteins and microorganisms. It is classified into serous crust (eosinophilic protein exudates), hemorrhagic crust (RBC’s), cellular crust (degenerative leucocytes mainly neutrophils), serocellular crust (mixture of serum or plasma or leucocytes) and palisadic crust (presence of leucocytic infiltration, pustules and parakeratosis organized in a horizontal manner).

It is characterized by irregular growth and development of hair follicles and associated glands.

The disease is characterized by irregular growth and development of hair follicles and associated glands.

Sebaceous gland hyperplasia: It is a rare disease of dogs characterized by high hair coat and underlying skin, greasiness and in mainly due to excessive greasiness followed by clumping of the hair coat.

Etiology

Pemphigus foliaceous is a bullous autoimmune skin disease of canines affect ing epidermis and hair follicles. The recorded targeted auto-antigen in canine pemphigus foliaceous is desmoglein 1 (Dsg 1). This auto-antibody binds to Dsg 1 which is a prominent component of desmosome in the superficial layer of epidermis and hair follicle. It may be due to loss of intercellular cohesion leading to acantholysis followed by formation of superficial vesicles and bul lae. The common sites for the development of pemphigus in dogs are dorsal lateral muzzle, temporal, planum nasale, pinnae, periorbital skin and paw pads.

The condition is one of the most common pruritic skin disease caused by hypersensitivity reaction to the flea salivary antigens. Type I immediate hypersensitivity, type II delayed hypersensitivity and cutaneous basophil hypersensitivity to the flea salivary antigens have been recorded. Late phase IgG mediated reaction also caused in this condition. It occurs in dogs mostly between 1 and 3 years of age.

Synonym – Cutaneous ancylostomiasis

Etiology

Hook worm dermatitis is uncommon or rare skin disease due to larval migration of the normal life cycle of Ancylostoma braziliensis and Ancylostoma caninum. It is mainly due to hypersensitive reactions against migrating third stage larvae in the distal extremities.