+ General Considerations
- SCC accounts for 5% of canine skin tumors and 15% of feline skin tumors
- Predisposition to unpigmented or lightly pigmented skin exposed to solar radiation
- Possible association with canine papillomavirus and abnormalities in tumor suppressor gene p53
- Firm and nodular masses which may be either proliferative or erosive and extend deeply into the dermis
- Sites: limbs, trunk, scrotum, and head and neck
- SCC tends to develop in lightly pigmented skin on the flank and abdomen in white English Bull Terrier, Dalmatian, Beagle, and Whippet breeds
- Preneoplastic changes include erythema, actinic necrosis, solar elastosis, and carcinoma in situ
- Cutaneous SCC is locally invasive with a low metastatic potential
- Multiple lesions are common varying from carcinoma in situ to more infiltrative and nodular lesions
- Cutaneous SCC is usually well differentiated, but anaplastic SCC may metastasize to regional lymph node and lung
+ Treatment
- Methods: surgical resection, radiation therapy, local hyperthermia, cryotherapy, and chemotherapy
- Retinoids (i.e., isotretinoin and etretinate) inhibit cell growth and induce cellular differentiation
- Retinoids are potent modulators of squamous differentiation in normal and malignant keratinocytes
- Etretinate is only effective against preneoplastic lesions
- Combination of isotretinoin and local hyperthermia are effective against early lesions
- Intralesional chemotherapy with 5-fluorouracil, cisplatin, BCNU, or methotrexate
- Antineoplastic effect of these agents associated with an intense inflammatory reaction and gloves should be worn during application and should not be applied to cats with SCC (neurotoxicity)
- Systemic chemotherapy inconsistent with response rates low and short-lived: mitoxantrone, actinomycin D, doxorubicin and cyclophosphamide, bleomycin, and cisplatin