Page 200 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Round Cell Tumours
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10.6 Cutaneous Lymphoma
VetBooks.ir Primary lymphoproliferative disease infiltrating the epidermis and/or cutaneous adnexa (epithe-

liotropic lymphoma) or the dermis (cutaneous non-epitheliotropic lymphoma).

Clinical features
• Uncommon cutaneous neoplasm of the dog and the cat, accounting for about 1%
and up to 2.8% of all skin tumours in dogs and cats, respectively.
• Age: it mostly occurs in older animals, with an average age of approximately 10 years
old in both species.
• The clinical presentation is variable and non-specific and could mimic other dermatopa-
thies. It may occur in the form of single or multiple nodules, plaques, ulcers, erythaemic
or exfoliative dermatitis, often covered by scaly plaques with focal hypopigmentation
and alopecia. In dogs, lesions are often pruritic. Mucocutaneous forms may involve the
gums, lips and anal mucosa. These often appear thick, ulcerated and inflamed.
• In advanced stages, peripheral lymph nodes, internal organs, peripheral blood and/or
bone marrow may be involved. When neoplastic lymphoid cells appear in the blood,
the condition is called Sezary syndrome.
• Over-represented canine breeds: Cocker Spaniel, Bulldog, Boxer, Scottish Terrier and
Golden Retriever.
• Cutaneous epitheliotropic lymphoma (CETL):
• T-cell (CD8+) immunophenotype.
• It is the most common form of cutaneous lymphoma in dogs. It is extremely rare
in cats.
• Neoplastic cells show affinity for the epithelial cells of the epidermis and adnexal
structures. If they are confined above the basement membrane of the epidermis
or the epithelium of adnexa, the disease is referred to as pagetoid reticulosis. This
form is not very common in the dog and cat. When the neoplastic cells involve
both the epithelium of the skin and the dermis, the form is known as mycosis
fungoides (from the mushroom-like appearance of the lesions).
• Cutaneous non-epitheliotropic lymphoma (NEL):
• T- or B-cell immunophenotype.
• Non-epitheliotropic lymphoma is the most common form of cutaneous lymph-
oma in cats; it is uncommon in dogs.
• Neoplastic cells are localized in the dermis with no involvement of the epidermis
and/or adnexa.
• Cutaneous lymphoma at injection sites (CLIS) is an uncommon form of non-
epitheliotropic lymphoma that has been reported in cats in the setting of sub-acute to
chronic inflammation induced by injections. Due to this, it is more common in the lateral
thorax and interscapular regions. Reported cases mostly have a B-cell immunopheno-
type and show marked angiotropism.
• A subcutaneous panniculitis-like T-cell lymphoma (SPTCL) has also been described
in dogs. In this type of lymphoma, the neoplastic cells selectively involve the subcutis.
• Little is known about the clinical behaviour of cutaneous lymphoma. However, the
non-epitheliotropic lymphoma seems to be more aggressive and more rapidly pro-
gressive than the epitheliotropic form.