Cat & Dog - Skin Lymphoid Tumours

These notes are provided to help you understand the diagnosis or possible diagnosis of cancer in your pet. For general information on cancer in pets ask for our handout What is cancer. If not already performed your veterinary surgeon may suggest certain tests to help confirm or eliminate the diagnosis, and to help assess treatment options and likely outcomes. Because individual situations and responses vary, and because cancers often behave unpredictably, science can only give us a guide. However information and understanding of tumours in animals is improving all the time.

We understand that this can be a very worrying time and we apologise for the need to use some technical language. If you do not understand anything, please do not hesitate to ask.

Lymphocyte biology

Lymphocytes are key cells in the body's ability to fight and prevent infection (immunity). Lymphocytes are found in tissues throughout the body, in the blood and in particular concentration in lymph nodes (lymph glands) and other 'lymphoid tissue'. Lymphocytes are of two main types, called 'T' lymphocytes and 'B' lymphocytes. Each plays a different role in immunity. Plasma cells, which make antibodies, develop from 'B' lymphocytes.

What is this tumour?

Lymphocytosis is a term used to describe abnormal accumulations of lymphoid cells in the dermis or subcutaneous tissue of the skin. Occasionally, the term 'pseudolymphoma' is used for these. They are non-cancerous but some may progress to be cancerous (neoplasia).

Dermal cutaneous lymphosarcoma is a malignant proliferation (growth) of abnormal lymphocytes, usually visible as nodules in the skin. It is often rapidly progressive. The disease spreads to the lymph nodes (glands) and later to other organs of the body.

Epitheliotropic lymphoma, (sometimes described by human terms including mycosis fungoides, pagetoid reticulosis and Sezary syndrome) has a very variable clinical presentation. Sometimes there are skin nodules but it may resemble an inflammatory skin disease with scaling, hair loss or secondary infection. The disease is progressive and spreads to lymph nodes.

Phasmacytomas are proliferations of plasma cells and are usually solitary and benign.

What do we know about the cause?

Little is known about the causes of these tumours.

Why has my animal developed this cancer?

Some animals have a greater tendency (genetic susceptibility) to cancer. Some breeds have far more cancers than others, often of specific types. The more divisions a cell undergoes, the more probable is a mutation so cancer is commoner in older animals. In some cases, an animal has been exposed to factors in the environment that cause or promote cancer. These include sunlight, some chemicals and some infections.

Are these common tumours?

These are uncommon tumours in dogs and cats. They are mainly in middle aged to older animals.

How will this cancer affect my pet?

Some of these present as plaques or swellings. Epitheliotropic tumours have a varied presentation, often looking like an inflammatory skin disease or primary hair loss problem. As the cancers spread, the local lymph nodes may swell. Epitheliotropic tumours often spread to the mouth.

Weight loss due to loss of body fat and muscle is common in the later stages of the malignant cancers. The immune system is often damaged. Some tumours induce signs that are not readily explained by local or wider spread of the tumours. These signs are due to abnormal hormone production by the cancers. These include increased blood calcium levels leading to loss of bone.

Epitheliotropic tumours can also start in the gut, liver and urinary bladder.

How is this cancer diagnosed?

Clinically, these tumours can be difficult to diagnose with specificity. Diagnosis relies upon microscopic examination of tissue.

Various degrees of surgical invasion may be needed such as needle aspiration, punch biopsy and full excision. Cytology is the microscopic examination of cell samples. This can be used for rapid or preliminary tests on lumps or nodules. More accurate diagnosis and diagnosis of non-nodular types with prediction of behaviour (prognosis) rely on microscopic examination of tissue (histopathology). This is done at a specialised laboratory by a veterinary pathologist.

What types of treatment are available?

There is no curative treatment for lymphoid cancers. Chemotherapy of various types may slow the progression or bring clinical relief but there is currently no firm evidence that treatment consistently improves survival times.

Symptomatic treatment of the skin disease signs due to the epitheliotropic type may make your pet more comfortable.

Plasmacytomas are usually cured surgically.

Can this cancer disappear without treatment?

Cancer rarely disappears without treatment but as development is a multi-step process, it may stop at some stages. The body's own immune system can kill cancer cells but it is rarely 100% effective. Occasionally, these tumours have phases of spontaneous remission.

How can I nurse my pet?

The dermal lymphoid tumours are rarely itchy and rarely ulcerate so there is little which can be done to help. Use of symptomatic skin care products may help to alleviate discomfort of the epitheliotropic type.

After surgery, the operation site needs to be kept clean and your pet should not be allowed to interfere with the site. Any loss of sutures or significant swelling or bleeding should be reported to your veterinary surgeon. If you require additional advice on post-surgical care, please ask.

How will I know how this cancer will behave?

Sadly, the lymphoid tumours are not curable diseases. Histopathology will give your veterinary surgeon the diagnosis that will indicate the type and how it is likely to behave. However, there is significant variation between animals in their response to the tumours and therapy. If epitheliotropic tumours are diagnosed at an early stage months (or occasionally years) of good quality life may remain but in others, the progress is very rapid and only weeks of quality life may remain.

Plasmacytomas are usually benign, even when multiple.

Are there any risks to my family or other pets?

No, these are not known to be infectious and are not transmitted from pet to pet or from pets to people.