CHAPTER 24 EPITHELIOTROPIC LYMPHOMA 367
Tumoral: solitary or multiple erythematous plaques, nodules, and masses;
lesions often scaly or crusted, may ulcerate; lesions may rarely cycle (Figures
24.8, 24.9)
Oral cavity ulceration: severe ulceration of gingiva, palate, and/or tongue (Fig-ures 24.10, 24.11):
Majority of lesions disseminated on the body (83.3%), localized on the head
(63%), footpads (26.6%), pruritus (40%), or lymph nodes (20%) (Figures
24.12–24.14)
Depigmentation caused by displacement and/or damage of melanocytes
Lesions throughout the skin; marked tendency for involvement of mucocu-
taneous junctions (lip, eyelids, nasal planum, anorectal junction, or vulva)
or oral cavity (gingiva, palate, or tongue); lesions can be limited to the
mucocutaneous junctions or oral mucosa.Exfoliative erythroderma; progression to the tumor stage is very rapid in dogs com-
pared to human beings.
Mucocutaneous and oral mucosa forms merge with chronicity.
Rarely the nodular form develops without a preexisting patch or plaque stage
(d’embleeform).
Nodular stage may occasionally progress to a disseminated form with lymph node
involvement, leukemia, and (rarely) other organs.
Sezary syndrome: rare; leukemic variant with simultaneous development of cuta- ́
neous lesions, invasion of peripheral lymph nodes by neoplastic lymphocytes, and
circulating tumor cells; generalized and severe erythroderma, scaling, alopecia, and
severe pruritus reported; visceral involvement causes systemic illness.Pagetoid reticulosis: rare; neoplastic lymphocytic infiltrate is confined to the epider-
mis and adnexal structures in the early stages of the disease and extends to the dermis
in the late stages; exfoliative erythroderma without nodules and masses; mucocuta-
neous junctions and footpads predominantly affected; exclusively gamma delta T cells
(Figure 24.15).DIFFERENTIAL DIAGNOSIS
Dermatophytosis
Demodicosis
Dermatoses, i.e., Feline thymoma-associated exfoliative dermatoses
Allergic dermatitis
Ectoparasitism (especially sarcoptid mites)
Cutaneous forms of lupus erythematosus
Erythema multiforme
Pemphigus vulgaris
Bullous pemphigoid
Vasculitis
Nonneoplastic chronic stomatitis (infectious)
Other cutaneous neoplasia: histiocytoma, cutaneous histiocytosis, mass cell tumor