Endocrine Tumours - Adrenal Cortex
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 veterinarian 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
Endocrine glands produce specialised chemicals called “hormones”. These regulate and integrate many activities to maintain internal stability of the body. The hormones pass directly into the blood to affect target cells elsewhere. The distinct endocrine glands are the adrenals, thyroid, parathyroids, pituitary glands and islets in the pancreas although certain hormones are also produced by many cells elsewhere in the body. The pituitary gland at the base of the brain links to other endocrine glands and regulates hormone production by the adrenals, thyroid and sexual organs as well as growth and our day to day cycles of activity (diurnal rhythm).
What are the adrenal glands?
The adrenals are a pair of distinct endocrine glands, located close to the kidneys.
Each adrenal gland has two parts.
The outer part (cortex) is controlled by a hormone (adrenocorticotrophic hormone, ACTH) from the pituitary gland. The cortex produces steroid hormones of several types. One interacts with the kidney to control salt concentrations in the body and a second group act as sex hormones. The third type has many actions including reduction of inflammation, healing and activity of the immune system. The hormone also controls carbohydrate and fat metabolism in conjunction with other hormones from the pancreas.
The inner part (medulla) of the gland originates from the same cells that in the embryo form the nervous system, and therefore not surprisingly it produces neuroendocrine hormones with effects similar to those of the sympathetic nervous system.
What are the tumours of the adrenal cortex?
Tumours of the cortex of the adrenal glands may be overgrowths (hyperplasias) or benign (non-spreading) or malignant (spreading) cancers. Usually they are producing hormones that will have secondary clinical effects elsewhere in the body.
What do we know about the cause?
Prolonged stimulation of the adrenal cortex is often the cause of development of these cancers with a continuous spectrum of abnormal change from small areas of hyperplasia to benign and then malignant cancer. The stimulation may be due to overproduction of pituitary hormones that control the gland, or excess of these or similar hormones from an external source such as medicines or chemicals in the environment. Sometimes disruption of the natural regulation of hormone production (‘feedback control’) by the gland results in over-stimulation. Cancer induction is a multistep process called ‘tumour progression’. Some cancers never progress past the first stages so remain benign. Others progress rapidly.
"Prolonged stimulation of the adrenal cortex is often the cause of development of these cancers with a continuous spectrum of abnormal change from small areas of hyperplasia to benign and then malignant cancer."
The reason why a particular pet may develop this, or any cancer, is not straightforward. Cancer is often seemingly the culmination of a series of circumstances which come together for the unfortunate individual.
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. In many cases, these tumours need prolonged stimulation to start growing and, sometimes, to enable them to persist.
Are these common tumours?
None of these tumours is common. Tumours of the pituitary, which produce the hormone (ACTH), results in over-stimulation of the adrenal cortex leading to clinical signs associated with adrenal cortical hormone excess. Such pituitary tumours are commoner than primary tumours of the adrenal itself. In dogs, benign tumours of the adrenal cortex are the commonest type and are seen in older animals. Adrenal tumours of all types are rare in cats.
How will these cancers affect my pet?
Clinical signs of primary pituitary tumours secondarily affecting the adrenal glands and of primary tumours of the adrenal cortex are the same. These signs include increased appetite and thirst, loss of hair, dry skin and “blackheads” on the belly. Some animals also have hard (calcium) masses in the skin on the neck and back with ulcers and formation of pus, redistribution of body fat and weakening of muscles so the abdomen sags. The immune system is damaged so infections persist for longer than normal. Some dogs are also diabetic. Some tumours of the adrenal cortex produce excessive sex hormones. Malignant adrenal cancers may spread through the body by invading the adjacent blood vessels and seeding new tumours in body cavities and other organs.
How are these cancers diagnosed?
Cancer is often suspected from clinical signs. Radiography (x-rays), ultrasound and MRI (magnetic resonance imaging) or CT (computerised tomography) scans may be useful in detecting the tumours, including metastases.
Blood tests help to indicate functional tumours of the pituitary and adrenal cortex. However, to identify the tumour type precisely, it is necessary to examine the tumour itself. This involves exploratory surgery, often with total removal of the tumour. The tissue samples are submitted for microscopic examination by histopathology. Specially prepared and stained tissue sections are made at a specialised laboratory where the slides are examined by a veterinary pathologist.
The histopathology report typically includes words that indicate whether a tumour is ‘benign’ (non-spreading, local growth) or ‘malignant’ (capable of spreading to other body sites). These, together with the origin or type of tumour, the grade (degree of resemblance to normal cells or ‘differentiation’) and stage (how large it is and extent of spread) indicate how the cancer is likely to behave.
The veterinary pathologist usually adds a prognosis (what will probably happen). This may include information on local recurrence or metastasis (distant spread).
What types of treatment are available?
Adrenocortical tumours are usually removed surgically, sometimes with medical treatment as well. Medical treatment, as for the pituitary tumours inducing secondary adrenal malfunction, is only successful if the cancer is still responding to pituitary hormones.
"Adrenocortical tumours are usually removed surgically, sometimes with medical treatment as well."
Can these cancers 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. Rarely, loss of blood supply to a cancer will make it die but this is rarely complete.
How can I nurse my pet?
After any surgery, you need to prevent your pet from interfering with the operation site and to keep it clean. Any loss of stitches or significant swelling or bleeding should be reported to your veterinarian. You may be asked to check that your pet can pass urine and faeces or to give treatment to aid this. If you require additional advice on post-surgical care, please ask.
Medical treatment of these tumours involves the use of toxic drugs so monitoring of your animal is essential. Good observation by you will enable this to be more accurate and improves the outlook because relapses are common. Please ensure you understand what you should check, how frequently and signs you should look out for.
How will I know how the cancer will behave?
This information will help you to understand the different types of tumours. Your veterinarian will be able to explain how the specific tumour in your animal is likely to respond to treatment and behave in the future.
Histopathology will give your veterinarian the diagnosis that also helps to indicate how a tumour is likely to behave. The veterinary pathologist usually adds a prognosis that describes the probability of local recurrence or metastasis (distant spread) for cancers.
When will I know if the cancer is permanently cured?
“Cure” has to be a guarded term in dealing with any cancer.
Adrenal cortical tumours that can be treated surgically may be cured, but it is more probable that on-going medical treatment will be necessary. The treatment needs monitoring and life expectancy is variable from days to ten years and averaging less than three years. Good observation by you, the owner, improves the outlook because relapses are common. Deaths are due to problems associated with the original disease (e.g. heart failure, infection, pancreatic disease such as diabetes) rather than related to drug toxicity.
Are there any risks to my family or other pets?
No, these are not infectious tumours and are not transmitted from pet to pet or from pets to people.
Adapted by Philip H Brain, BVSc, CMAVA, FACVSc (small animal medicine), FAVA © Copyright 2015 LifeLearn Inc. Used and/or modified with permission under license.