Skin LSA

+ General Considerations

• B cell or mixed cutaneous LSA that can either be primary or multicentric LSA
• No breed or site predilection
• Single or multiple lesions with plaque, pustule, or ulcerative skin disease and resultant pruritis
• Nodules with thick crust and underlying ulceration and erythematous rim

+ Treatment

Surgical resection ± systemic chemotherapy

+ Prognosis

Response to chemotherapy is usually poorer than multicentric LSA mycosis fungoides and cutaneous LSA in cats is associated with very poor prognosis as response to therapy is rare

+ General Considerations

• T cell cutaneous LSA
• Breed predisposition: Poodle and Cocker Spaniel
• Mycosis fungoides has been reported in cats
• Site: epidermis, superficial dermis, and periadnexa (= epidermotrophic)
• Gross Appearance: plaque or nodular lesion

+ Clinical Signs

• Protracted clinical course with 3 clinical stages:
• Premycotic (erythroderma) stage: eczema, erythema, pigmentation or depigmentation, telangiectasis, atrophy, alopecia, and variable pruritis with trunk or neck involvement initially ± primary mucocutaneous junction or entire body involvement
• Mycotic (plaque) stage: erythematous, raised, thickened, and firm plaques that may be ulcerative and exudative
• Tumor stage: proliferative, protruding nodules ± ulceration and metastasis to regional lymph nodes and internal organs
• Secondary pyodermas and lymphadenomegaly secondary to chronic dermatitis is common

+ Sezary Syndrome

• Leukemic variant of mycosis fungoides characterized by circulating malignant helper T cells
• Mycosis fungoides complicated by Sezary syndrome is characterized by splenomegaly, lymphadenopathy, and cyclic episodes of generalized erythroderma
• Sezary cells are identified in the peripheral blood of 100% of humans in the premycotic stage and 40% of the mycotic and tumor stages
• Bone marrow does not become infiltrated with neoplastic cells in either mycosis fungoides or Sezary syndrome

+ Diagnosis

Biopsy although premycotic and mycotic stages are more reliable than tumor stage

+ Treatment

• No uniform success with multiple treatment regimens
• Lesions limited to the skin can be treated with:
• Topical nitrogen mustards (i.e., mechiorethamine or BCNU)
• Vitamin A analogues (i.e., 13-cis-retinoic acid)
• Electron radiation therapy
• Photodynamic therapy (with psoralen UVA)
• Intravenous and intralesional fibronectin (acts as opsonin in areas of disrupted tissue and chemotactically draws macrophages into tissue)
• Intradermal placental lysate
• Prednisone
• Systemic chemotherapy should be attempted with disseminated mycosis fungoides but results are usually poor

+ Prognosis

Poor with most animals euthanased prior to tumor stage development due to uncontrollable skin lesions