CONDITION
Cutaneous Lymphoma
Cutaneous lymphoma is a condition in which a type of immune cell called a lymphocyte becomes cancerous and accumulates in the skin. These cells normally circulate through the body as part of the immune system, but in cutaneous lymphoma they multiply abnormally and gather in patches, nodules, or more widespread areas of the skin. It can occur in dogs and cats, though the appearance and behaviour of the condition differ between species. Owners most often notice raised lumps, thickened patches of skin, reddened areas, ulceration, or changes in pigmentation that may appear in one location or several. The signs can sometimes resemble other skin conditions such as infection, allergy, or benign growths, which is why the condition is often investigated over time. In some cases, changes elsewhere in the body may develop later, but the skin is the primary site of concern at the outset. This page explores what signs may be observed, what is happening at a cellular level, how the condition is investigated through biopsy and staging, and what treatment approaches exist. The aim is to orient you to the shape of the condition and the decisions that may unfold over time.
Why this matters now
Cutaneous lymphoma tends to appear in middle-aged to older dogs, often between seven and eleven years, though younger animals can occasionally be affected. Certain breeds, including Cocker Spaniels, Boxers, and Scottish Terriers, appear more frequently in case series, though the condition occurs across many breeds and in mixed-breed dogs as well. In cats, the condition is less common overall and may appear at various ages, sometimes in association with prior viral exposure, though many cases arise without an identifiable trigger.
The condition may begin as a single small nodule or patch that persists despite treatment for presumed infection or allergy, or it may present with multiple lesions at the outset. Progression varies widely between individuals; some animals develop new areas of involvement over weeks to months, whilst others remain relatively stable for extended periods. The skin may remain the only site of disease throughout, or internal involvement may develop later, a pattern that cannot be predicted reliably at the time of diagnosis.
Signals & patterns
Early signals
Raised nodules or plaques
Firm, raised areas may appear on the trunk, head, or limbs, sometimes feeling slightly thickened beneath the skin. They may be skin-coloured, reddened, or darker, and can be mistaken for cysts or benign growths.
Persistent reddened patches
Areas of redness that do not resolve with treatment for infection or allergy may remain for weeks or gradually expand. The skin in these areas may feel slightly thicker than surrounding tissue.
Scaling or flaking
The surface of affected areas may become scaly, with fine or coarse flakes, sometimes resembling dry skin or seborrhoea. This pattern can persist despite topical treatment.
Localised hair loss
Hair may thin or fall out over nodules or patches, leaving smooth or mildly textured skin beneath. The loss tends to occur gradually rather than suddenly.
Later signals
Ulceration or crusting
Lesions may break down, forming open sores that weep or crust over. These areas can become secondarily infected, adding odour or discharge to the clinical picture.
Widespread skin thickening
The skin may become diffusely thickened, sometimes with a leathery texture, affecting large areas of the body. This change can alter the animal's appearance and may be accompanied by itching or discomfort.
Mucosal involvement
The gums, lips, or nasal passages may develop nodules or colour changes, appearing swollen or ulcerated. This pattern can affect eating or breathing in some cases.
Generalised changes
Weight loss, reduced appetite, or lethargy may emerge over time, particularly if the disease extends beyond the skin. These signs are not specific but reflect a broader shift in the animal's condition.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
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