What is cutaneous lymphoma?
A cutaneous lymphoma is a tumoral proliferation of lymphocytes (cells of the immune system) within the skin tissue. In other words, it is a malignant skin tumor.
There are actually two forms of cutaneous lymphoma: epitheliotropic cutaneous lymphoma and non-epitheliotropic cutaneous lymphoma.
Cutaneous epitheliotropic lymphoma
Cutaneous epitheliotropic lymphoma is a rare skin condition in dogs linked to an infiltration of tumor T lymphocytes.
In dogs, the most frequently encountered is mycosis fungoides, a form of epitheliotropic cutaneous lymphoma which initially affects the skin and/or mucous membranes of the animal under very variable clinical pictures and which can develop subsequently spread to the lymph nodes and internal organs of the animal.This form of cutaneous lymphoma is seen mainly in very old dogs. The Cocker Spaniel, the Coton de Tulear, the Berger des Pyrénées, the Bichon Frize and the Airedale terrier could be predisposed to it, as could dogs that suffer from atopic dermatitis.
Cutaneous epitheliotropic lymphoma can also be associated with leukemia (presence of tumor cells in the blood). This is called Sézary syndrome.
More rarely, it can only affect the epidermis and we then speak of pagetoid lymphoma.
Cutaneous non-epitheliotropic lymphoma
Epitheliotropic cutaneous lymphoma is an infiltration of tumor lymphocytes in the skin and mucous membranes. These are rare malignant tumors that mainly affect older dogs and to which the Saint Bernard, the Boxer, the Irish Setter, the Cocker Spaniel, the German Shepherd, the Scottish Terrier and the Golden Retriever are predisposed.
What are the symptoms of cutaneous lymphoma in dogs?
In dogs, cutaneous lymphomas can manifest themselves in very variable forms. The first symptoms are generally not very specific and can evoke many other skin conditions.
Depending on its form, a cutaneous lymphoma can manifest as:
- erythema, in other words redness of the skin that can appear in patches,
- depigmentation of the skin, especially at the junctions between the skin and the mucous membranes, the nose or the pads,
- scaling (appearance of “dandruff”),
- appearance of nodules on the skin, ulcers, scabs and/or erosions,
- skin hemorrhages,
- localized alopecia (loss of hair),
- a sometimes intense pruritus (itchy feeling of the skin).
These lesions can coexist on the same animal at the same time or follow one another over time. An impairment of the general condition of the dog can also be observed sometimes.
How is cutaneous lymphoma diagnosed in dogs?
Faced with lesions that could be reminiscent of cutaneous lymphoma, the veterinarian will first focus on performing a cytological examination by puncturing a skin lesion with a fine needle.
If the results of the cytological examination are doubtful, the veterinarian will obtain a diagnosis of certainty using a histopathological examination. To do this, the veterinarian will perform several skin biopsies on the animal.
If the histopathological examination confirms the presence of lymphoma, the veterinarian will then carry out an extension assessment including a chest X-ray, an abdominal ultrasound and a spinal tap or biopsy.
What treatment for cutaneous lymphoma in dogs?
Treatment depends on the form of canine cutaneous lymphoma.
It may involve only chemotherapy for diffuse and oral forms or surgery followed by adjuvant chemotherapy for nodular and plaque forms.
In all cases, the prognosis for dogs with cutaneous lymphoma remains quite poor even if the treatments can lead to a temporary remission.