Lymph node cancer – when does my dog need chemotherapy?

Unfortunately, our pets are not immune to cancer either. Malignant lymphoma is a malignant tumor that originates in cells of the immune system. Since these cells are mainly found in lymph glands, it is also referred to as lymph gland cancer.

INHALT
Cause and origin Classification Symptoms Diagnosis Treatment Forecast
Cause and origin

As with many types of cancer, the causes or triggers of this type of tumor are unknown. Starting in the cells of the immune system, it first attacks the lymphatic organs (lymph nodes, spleen, thymus, bone marrow). As the disease progresses, non-lymphatic organs are also affected and eventually leukemia develops, which means that tumor cells are present in the blood.

Classification

Different forms of lymphoma are defined depending on where they occur and how far they have spread.

Based on where it occurs, a distinction is made between:

Multicentric lymphoma

The most common form, involving several organs, usually the lymph nodes, spleen, and liver. The bone marrow may also be affected.

Gastrointestinal lymphoma

Limited to the gastrointestinal tract. The intestinal lymph nodes are affected.

Thymus lymphoma

The tumor is confined to the chest and is usually located in front of the heart. Fluid accumulation in the chest is possible.

Skin lymphoma

Nodular skin changes occur.

Brain lymphoma

Tumor cells are found in the cerebrospinal fluid.

Depending on the extent of spread, the disease is divided into five stages, starting with the involvement of a single lymph node in stage 1, progressing to organ involvement in stage 4, and ending with stage 5, which includes bone marrow involvement.

Diagram of lymph nodes in dogs
Lymph nodes of the: 1 lower jaw | 2 larynx | 3 parotid gland | 4 neck | 5, 6 armpit | 7 iliac | 8 groin | 9 popliteal fossa
Symptoms

Due to the many different possible locations of the tumor, a wide variety of symptoms can be observed. At the onset of the disease, nodular changes in the lymph nodes in the head area often occur, which can be felt when stroking or touching the animal. The affected animals usually do not show any signs of general discomfort.

The main symptoms of gastrointestinal lymphoma can include chronic diarrhea, vomiting, and weight loss. Thymus lymphoma causes difficulty breathing, coughing, and fatigue due to the tumor mass in the chest. If the central nervous system is affected, seizures, disturbances of consciousness, circling, or disorientation may occur. However, cases with very nonspecific general symptoms such as loss of appetite, apathy, reluctance to move, fever, and emaciation may also occur from the outset.

Dog with swollen lymph node
Diagnosis

Your preliminary report and the clinical examination usually provide the veterinarian with important information about the location and spread of the disease. If the symptoms are very unclear, various further examinations may be necessary to diagnose lymphoma accurately.

A blood test is always part of standard tumor diagnostics. X-rays, CT scans, MRIs, or ultrasounds can provide important clues about the spread of the tumor. The veterinarian will decide on a case-by-case basis to what extent these are helpful and necessary. With the help of fine needle aspiration (cell removal using a hollow needle), cell samples can be taken from altered lymph nodes and examined for malignant cells. However, these can be most reliably detected in a tissue sample obtained by biopsy.

Even though malignant lymphoma in its final stages can lead to leukemia, the "lymphatic leukemia" originating in the bone marrow must be distinguished from lymphoma, which is not always easy given the similar symptoms. Organs may also be affected in leukemia, but lymph node enlargement is not usually found.

Treatment

Since most lymphomas in dogs are malignant and fast-growing, treatment must be started as soon as possible. Various types of chemotherapy drugs (medications that kill cancer cells) are used with the aim of shrinking the tumor (remission). Your veterinarian will create an individual treatment plan based on the course of the disease, which often must be carried out over several weeks

Forecast

Complete cure of lymphoma is still only possible in a few cases. The goal of tumor therapy is to prolong the dog's life by suppressing tumor growth. However, relapses must always be expected, even if there may be several months to several years between individual episodes. During the course of treatment, the tumor cells may also develop resistance to the drugs, which makes treatment even more difficult. The average survival time of a dog with lymphoma undergoing chemotherapy is twelve months, in some cases longer.