+ 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