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Squamous cell carcinoma
Squamous cell carcinoma (SCC) are one of the most common neoplasms of the dog.
These tumors originate in squamous epithelial cells located in the skin, kidneys and reproductive tact, intestines (oral to rectal) and mucosal surfaces of most organs, although the skin, oral cavity and digits are the most common sites in dogs.
Common locations of cutaneous squamous cell carcinomas include the legs, scrotum, perineum, inguinal region (truncal solar dermatitis), nasal planum, and various lightly pigmented areas.
Cutaneous squamous cell carcinomas are loosely categorized as follows:
- Cutaneous squamous cell carcinoma (actinic/solar keratosis)
- Subungual Squamous Cell Carcinoma
- Oral squamous cell carcinoma
- Multicentric SCC (Bowen's disease) - very rare in dogs
These tumors generally grow slowly, but are locally invasive, commonly found in older dogs.
Although chronic inflammation plays an important role in the pathogenesis of squamous cell carcinoma, other factors are often involved. Ocular squamous cell carcinomas have been associated with canine papillomavirus, and cutaneous SCCs are commonly observed in the inguinal region of dogs due to UV exposure. Urban pollutants may also increase the risk for tonsillar SCCs.
Clinical signs depend on the organ involved, but localized ulceration, proliferative, raised cauliflower-shaped red plaques are a common finding. Digital SCCs commonly result in variable lameness and digital ulceration. Nasal tumors can cause nasal discharge and sneezing and oral SCCs usually present as ptyalism, gingival bleeding, anorexia, dysphagia and halitosis. Intestinal and rectal SCCs usual present with gastrointestinal signs; tenesmus, rectal bleeding and weight loss.
Regional lymphadenopathy is common as is secondary bacterial infections and pyoderma in cutaneous lesions. Metastases to bone are common and secondary osteomyelitis in such cases also occurs in some cases.
Diagnosis is usually confirmatory on visual inspection (via laparotomy with visceral tumors) and histopathological analysis of biopsied material. These tumors have a characteristic appearance under light microscopy, with islands, cords and trabeculae of invasive epithelial cells associated intimately with the overlying epidermis and breaching of the basal lamina zone. Keratin pearls (lamellae of keratin within the tumor) are commonly observed, formed by the invasive cells.
Immunohistochemistry usually shows binding to calretinin and cytokeratins.
Histological classifications include:
- papillary squamous cell carcinoma
- basaloid squamous cell carcinoma
- adenosquamous carcinoma
- spindle cell carcinoma
Treatment in localized skin lesions is usually curative but recurrence in adjacent areas is not uncommon.
Adjunct therapy such as cryotherapy, radiation therapy, photodynamic therapy and intratumoral chemotherapy may assist recovery and recurrence.
- Your own vet
- Uni of Pennsylvania
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