CONDITION
Adrenocortical Carcinoma
Adrenocortical carcinoma is a cancer that arises from the outer layer of the adrenal gland — a small structure that sits near the kidney and produces hormones involved in metabolism, stress response, and fluid balance. In dogs, this type of tumour can behave in two broad ways: it may produce excessive amounts of hormones (most often cortisol, leading to signs similar to Cushing's syndrome), or it may grow without obvious hormonal activity, in which case signs relate to the mass itself or to spread elsewhere in the body. Owners often arrive at this page after imaging has identified a mass on or near the adrenal gland, or because their dog has been investigated for persistent weight gain, increased thirst, muscle weakness, or a swollen abdomen. Some dogs show no outward signs at all, and the finding is incidental during imaging for another reason. The behaviour of these tumours varies: some remain slow-growing and localised for months or years, while others invade nearby structures or spread to the liver, lungs, or lymph nodes relatively early. This page explores the signals that may suggest adrenocortical carcinoma, what is happening at a tissue and hormonal level, how the condition is investigated through imaging and laboratory tests, and the range of approaches that exist — from surgical removal to medical management of hormone excess or monitoring in cases where intervention carries significant risk.
Why this matters now
Adrenocortical carcinoma tends to appear in middle-aged to older dogs, most commonly between eight and eleven years of age, though younger animals can occasionally be affected. Certain breeds — including Poodles, Dachshunds, Labrador Retrievers, and German Shepherd Dogs — appear in clinical reports more frequently, but the tumour can arise in any breed or crossbreed. There is no clear environmental or dietary trigger; the condition appears to develop as a consequence of spontaneous changes in the cells of the adrenal cortex over time.
The course of adrenocortical carcinoma varies considerably between individuals. Some tumours remain relatively contained within the adrenal gland for months or even years, growing slowly and causing few outward changes, particularly if they do not produce excess hormone. Others invade the large blood vessels adjacent to the adrenal gland — most notably the vena cava — or spread to the liver, lungs, or abdominal lymph nodes within weeks to months of onset. Hormone-secreting tumours may produce signs that progress gradually, with metabolic changes accumulating over months, while non-functional tumours may only become apparent when the mass itself causes discomfort or when metastatic spread is detected.
Signals & patterns
Early signals
Increased thirst and urination
A dog may begin drinking noticeably more water and asking to go outside more often, or having accidents indoors despite previously reliable house-training. This pattern often develops gradually and can be attributed to excess cortisol affecting the kidneys' ability to concentrate urine.
Increased appetite with weight gain
The dog may seem persistently hungry, seeking food more actively or scavenging in ways that were not typical before. Weight may increase, particularly around the abdomen, even without a change in the amount fed.
Thinning coat or poor regrowth
The hair coat may become thinner, patchy, or slow to regrow after clipping or a seasonal shed. The skin itself may appear thinner or more fragile, and small blood vessels may become visible beneath the surface.
Reduced stamina or muscle weakness
An owner may notice the dog tires more easily on walks, has difficulty jumping onto furniture or into the car, or appears less steady on the back legs. Muscle mass may visibly decrease, particularly over the spine and hindquarters.
Abdominal enlargement
The belly may appear rounder or more pendulous, sometimes described as pot-bellied. This can result from fat redistribution, liver enlargement, or weakening of the abdominal muscles, and may develop over weeks to months.
Later signals
Persistent panting or restlessness
The dog may pant heavily even at rest or during cool weather, and may appear unable to settle comfortably. This can reflect both metabolic changes and discomfort from an enlarging mass or metastatic disease.
Visible abdominal mass or asymmetry
In some cases, a firm swelling may become palpable or visible on one side of the abdomen, particularly in lean dogs. This may indicate a large primary tumour or enlargement of the liver due to metastatic spread.
Collapse or sudden weakness
Acute episodes of weakness, collapse, or pale gums can occur if the tumour invades a major blood vessel and causes bleeding into the abdomen, or if a blood clot forms and dislodges. These episodes may be brief or prolonged.
Coughing or laboured breathing
Respiratory signs may develop if the tumour has spread to the lungs. The dog may cough intermittently, breathe more rapidly, or show reduced tolerance for exercise.
Click to read about the biological mechanisms
How this is usually investigated
Investigation typically begins with a clinical history and physical examination, particularly when signs such as increased thirst, abdominal distension, or muscle weakness are present. If an adrenal mass is suspected or discovered incidentally, further work focuses on characterising the mass itself, assessing whether it is producing excess hormone, and determining whether spread has occurred. The sequence and depth of testing depend on the individual animal's signs, the clarity of initial findings, and the owner's willingness to pursue different management paths.
Abdominal ultrasonography
Computed tomography or magnetic resonance imaging
Blood biochemistry and endocrine testing
Thoracic radiography
Fine-needle aspiration or biopsy
Options & trade-offs
Management is shaped by the tumour's behaviour, the presence or absence of hormone secretion, the extent of invasion or spread, and the individual dog's overall health and temperament. Some owners and animals pursue surgical removal when the mass is localised and accessible; others focus on controlling hormone excess or on monitoring when intervention carries high risk or when metastatic disease is already present. No single approach fits all cases, and decisions often evolve as the picture becomes clearer over weeks to months.
Surgical removal (adrenalectomy)
Adrenalectomy involves removal of the affected adrenal gland, and sometimes adjacent invaded tissue, through open abdominal surgery. When the tumour is confined to the gland and has not invaded the vena cava or spread to distant sites, removal can eliminate the source of hormone excess and may offer prolonged survival. The procedure is technically demanding, particularly when vascular invasion is present, and is typically performed by surgeons with experience in soft-tissue or oncological surgery.
Trade-offs: Perioperative complications can include haemorrhage, blood clot formation, acute collapse, or transient disturbances in electrolyte balance, particularly if the remaining adrenal gland has been suppressed by long-term cortisol excess. Recovery can take several weeks, and surgery does not prevent recurrence or spread if microscopic disease is already present. Dogs with large, invasive, or metastatic tumours, or with significant concurrent illness, may not be candidates.
Medical management of cortisol excess
Trilostane or mitotane can be used to suppress cortisol production in dogs with hormone-secreting tumours, reducing signs such as increased thirst, muscle weakness, and abdominal distension. These medications do not shrink the tumour or prevent spread, but they can improve quality of life and metabolic control when surgery is not pursued or while awaiting surgery. Dosing is individualised and adjusted based on regular monitoring of cortisol levels and clinical response.
Trade-offs: Medical management requires ongoing monitoring and dose adjustment, and does not address the mass itself or the risk of invasion or metastasis. Some dogs experience side effects such as lethargy, vomiting, or electrolyte disturbances, and response is variable. If the tumour is non-functional, these medications offer no benefit.
Monitoring without intervention
In cases where the tumour is small, non-functional, and discovered incidentally, or where the dog is elderly or has other health conditions that make surgery or medical treatment high-risk, observation with serial imaging and clinical assessment may be the chosen path. This allows time to see how the tumour behaves and whether signs develop, without committing to intervention at the outset.
Trade-offs: Monitoring does not slow tumour growth or prevent complications such as vascular invasion or rupture, and some tumours progress more quickly than anticipated. It requires periodic imaging and clinical review, which can add cost and may not suit owners who prefer a more active approach. If signs do develop, options may become more limited as the disease advances.
Chemotherapy or targeted therapy
Chemotherapy using agents such as mitotane at high doses, or investigational protocols involving platinum-based drugs or targeted therapies, has been explored in dogs with inoperable or metastatic adrenocortical carcinoma. These approaches aim to slow tumour growth or control hormone production when surgery is not feasible. Evidence for efficacy is limited, and protocols are not standardised.
Trade-offs: Response rates are variable and often modest, and treatment can carry side effects including nausea, immune suppression, and kidney or liver toxicity. Access to these approaches may require referral to a specialist oncology service, and the time and financial commitment can be substantial. Many owners and animals find the balance of potential benefit and burden difficult to judge without trial.
Palliative and supportive care
When the tumour is advanced, metastatic, or when the dog is not a candidate for surgery or medical suppression of hormone production, care may focus on managing individual signs such as pain, fluid accumulation, or weakness. This can include analgesia, dietary adjustments, physiotherapy, or short courses of corticosteroid supplementation if the remaining adrenal tissue is insufficient.
Trade-offs: Palliative approaches do not alter the course of the disease, and quality of life may decline as the tumour progresses. Some signs, such as breathlessness from pulmonary metastases or acute collapse from vascular rupture, can be difficult to control. Conversations about comfort and the point at which further intervention may not serve the animal's interests become increasingly relevant.
Common misconceptions
"If my dog has an adrenal tumour, it will always show the classic signs of Cushing's syndrome."
Many adrenocortical carcinomas do not produce excess cortisol and therefore do not cause the increased thirst, pot-bellied appearance, or hair loss associated with Cushing's syndrome. In these non-functional tumours, signs relate to the physical presence of the mass or to spread to other organs, and some dogs remain entirely asymptomatic until the tumour is found incidentally on imaging.
"Surgery will cure my dog completely if the tumour is removed."
Surgical removal can offer prolonged survival and resolution of hormone-related signs when the tumour is localised and has not spread, but it does not guarantee cure. Microscopic spread may already be present at the time of surgery, and recurrence or metastasis can occur months to years later. The outcome depends on the tumour's biological behaviour, the completeness of removal, and whether invasion into blood vessels has occurred.
"Medication can shrink the adrenal tumour and avoid the need for surgery."
Drugs such as trilostane or mitotane suppress cortisol production but do not reduce the size of the tumour or prevent its growth or spread. They are used to manage the metabolic consequences of hormone excess, not to treat the cancer itself. If control of the mass or prevention of metastasis is the goal, surgery remains the approach with the potential to remove the tumour entirely.
Related conditions
Adrenal Tumours
Adrenocortical carcinoma is one specific type of adrenal tumour, distinguished by its malignant behaviour and origin from the outer cortex of the gland. The broader adrenal tumours page covers the range of growths that can develop in this organ, including those from the inner medulla and benign forms, providing context for how different tumour types in the same gland can behave.
Pheochromocytoma in Dogs
Pheochromocytoma arises from the inner portion of the adrenal gland—the medulla—rather than the cortex, and produces different hormones (adrenaline and related compounds) instead of cortisol or sex hormones. Both tumour types can present as adrenal masses on imaging, and distinguishing between them often requires a combination of hormonal testing and careful evaluation of clinical signs.
Atypical Cushings in Dogs
Some adrenocortical carcinomas produce excessive amounts of sex hormones such as progesterone or androstenedione rather than cortisol, leading to a hormonal pattern similar to that seen in atypical Cushing's. In both situations, signs may relate to these non-cortisol hormones, and the distinction often rests on imaging findings and the presence or absence of a visible adrenal mass.
Pituitary Macroadenoma
Pituitary macroadenomas can drive excessive cortisol production by signalling the adrenal glands to overproduce hormone, leading to Cushing's syndrome without a primary adrenal tumour. When a dog presents with signs of cortisol excess, distinguishing between a pituitary-driven process and an adrenal tumour such as adrenocortical carcinoma is a central part of the diagnostic pathway.
Steroid Hepatopathy
Dogs with cortisol-secreting adrenocortical carcinoma may develop changes in the liver consistent with steroid hepatopathy, as prolonged exposure to high cortisol levels can alter liver enzyme activity and cause the liver to enlarge. The hepatopathy in these cases is a consequence of the hormone excess rather than a separate liver disease.
Adrenocortical carcinoma sits at the intersection of endocrine disease and cancer, and understanding both aspects can help frame the range of outcomes and approaches. The Longevity & Healthspan pillar offers context on how age-related changes in tissue regulation contribute to tumour development, and on the broader questions of surgical candidacy and quality of life in older dogs. If your dog's investigation has identified an adrenal mass, the conversations about imaging findings, hormone testing results, and the balance of intervention and observation may be useful to revisit as the picture becomes clearer over time.