Mammary Tumours in Cats: Signs, Surgery, Treatment and Prognosis

Mammary Tumours in Cats: Signs, Surgery, Treatment and Prognosis

By Dr Duncan Houston

A mammary tumour in a cat may begin as a lump no larger than a pea. The cat may be eating normally, behaving normally and showing no sign that anything serious is happening.

This is not a lump to monitor casually for several months.

Approximately 80% to 90% of feline mammary tumours are malignant, and tumour size is one of the strongest predictors of outcome. The best opportunity for successful treatment is usually while the tumour is still small, before it has invaded surrounding tissue or spread through the lymphatic system.

Quick Answer

Any new lump along a cat’s mammary chain should be examined by a veterinarian within the next few days. Most feline mammary masses are malignant, and early staging followed by appropriately planned mastectomy offers the strongest chance of long-term control.

Do not wait for the lump to become painful, ulcerated or visibly large. Open-mouth breathing, marked breathing effort, uncontrolled bleeding, collapse or profound weakness require emergency veterinary care.

What Is a Mammary Tumour?

Cats normally have four pairs of mammary glands, making eight glands in total. They extend in two rows from the chest to the groin.

A mammary tumour develops when cells within one of these glands begin dividing abnormally. A cat may have:

• One isolated tumour

• Several tumours within one mammary chain

• Tumours affecting both sides

• A tumour involving the nipple

• Diffuse swelling rather than one obvious lump

• A tumour that has extended into the skin, muscle or lymphatic system

The most common malignant mammary tumours are carcinomas and adenocarcinomas. Different histological subtypes exist, and some behave more aggressively than others.

Although benign mammary lesions occur, a mammary mass in an adult or senior cat should be treated as potentially malignant until histopathology proves otherwise.

What Does a Mammary Tumour Feel Like?

Early tumours are commonly:

• Firm

• Round or irregular

• Located directly beneath or beside a nipple

• Attached to the mammary tissue

• Painless

• Only a few millimetres across

• Similar in texture to a small pebble beneath the skin

More advanced tumours may be:

• Fixed to the abdominal wall

• Irregular or multilobulated

• Rapidly increasing in size

• Ulcerated

• Bleeding

• Producing discharge

• Surrounded by swollen or reddened skin

• Painful

• Associated with several nearby nodules

A small mammary carcinoma can look disappointingly unimpressive. Waiting for it to look dangerous defeats the entire point of early detection.

What Are the Signs of Mammary Cancer in Cats?

The first sign is usually a lump noticed while stroking the cat or during a veterinary examination.

Other signs include:

• Enlargement of one nipple

• Thickening beneath a nipple

• Multiple small nodules along the abdomen

• A firm mammary gland

• Redness or warmth

• Skin ulceration

• Bleeding or discharge

• Persistent licking at the area

• Pain when the abdomen is touched

• Reduced grooming

• Reduced appetite

• Weight loss

• Lethargy

• Enlarged lymph nodes

• Swelling of a leg caused by impaired lymphatic drainage

If cancer has spread to the chest, signs may include:

• Faster breathing at rest

• Increased breathing effort

• Reduced activity

• Open-mouth breathing

• Coughing, although coughing is less common in cats than many owners expect

• Poor appetite

• Weight loss

• Collapse

A cat with pulmonary metastasis can appear normal until the disease is relatively advanced. This is why chest imaging is recommended before major surgery even when breathing appears normal.

What Is Inflammatory Mammary Carcinoma?

Inflammatory mammary carcinoma is a rare but particularly aggressive presentation.

Instead of one clearly defined lump, the cat may develop:

• Diffuse mammary swelling

• Red, warm or thickened skin

• Pain

• Skin oedema

• Ulceration

• Swelling extending along much of the abdomen

• Rapid progression over days or weeks

It may initially resemble mastitis, infection or trauma. The inflammation is caused by extensive cancer invasion within the small lymphatic vessels of the skin.

Inflammatory mammary carcinoma generally carries a grave prognosis. Radical surgery is often not appropriate because the disease is already diffusely distributed through the skin and lymphatic system. Biopsy, staging and early oncology consultation are important.

Can Male Cats Develop Mammary Cancer?

Yes, although it is uncommon.

Mammary carcinoma in male cats can behave just as aggressively as it does in females. In a retrospective study of 39 male cats, local recurrence was common and tumour size and lymphatic invasion were associated with a poorer outcome. Some affected males had previously received progestogen medication.

A mammary lump in a male cat should therefore not be dismissed because the patient does not fit the usual profile.

How Worried Should You Be?

Risk level	What you may notice	What to do
Suspicious but stable	One small, firm lump with normal appetite, breathing and behaviour	Arrange a veterinary examination within the next few days
Moderate concern	Multiple lumps, a tumour approaching 2 cm, recent growth or mild fixation to deeper tissue	Arrange prompt staging and surgical consultation
High concern	Tumour larger than 2 to 3 cm, rapid growth, ulceration, bleeding, pain, enlarged lymph nodes or leg swelling	Seek same-day or next-day veterinary assessment
Critical	Open-mouth breathing, marked respiratory effort, collapse, uncontrolled bleeding, blue or grey gums or inability to stand	Go to an emergency veterinary hospital immediately

A small, comfortable lump is not usually a middle-of-the-night emergency. It is still time-sensitive because the treatment options and prognosis worsen as tumour size and stage increase.

What Causes Mammary Tumours in Cats?

The exact cause is not completely understood, but hormonal exposure is an important part of feline mammary carcinogenesis.

Reproductive hormones

Intact female cats are at greater risk than cats spayed early.

A case-control study found that:

• Cats spayed before six months of age had an approximately 91% lower risk than intact cats

• Cats spayed before one year of age had an approximately 86% lower risk

• Having kittens did not reduce the risk

The strongest evidence of protection therefore relates to spaying before the first year of life. Claims of a precise protective percentage from spaying later in life are less secure and should not be oversold.

Age

Most malignant mammary tumours are diagnosed in mature and senior cats, commonly around 10 to 12 years of age.

Younger cats can still develop mammary lesions, particularly hormonally driven fibroadenomatous hyperplasia, but a new mammary mass in an older cat is considerably more concerning.

Breed

An older epidemiological study found that Siamese cats had approximately twice the risk of mammary carcinoma and tended to be diagnosed at a younger age than other cats. Breed alone cannot predict whether an individual lump is malignant, and subsequent populations have not always shown identical breed patterns.

Progestogen medication

Synthetic progestogens have been associated with mammary gland enlargement and mammary neoplasia in several feline populations.

Tell your veterinarian about any previous:

• Heat-suppression medication

• Progestogen tablets or injections

• Hormonal skin treatment

• Long-term hormonal therapy

This history is particularly important in male cats and younger cats with mammary enlargement.

Does Having Kittens Protect a Cat From Mammary Cancer?

No.

The available feline evidence did not find a protective effect from pregnancy or having litters. Allowing a cat to have one litter before spaying does not provide proven mammary-cancer protection.

Early spaying remains the most effective recognised preventive measure.

Can a Spayed Cat Still Develop Mammary Cancer?

Yes.

Spaying reduces risk most strongly when performed early, but it does not reduce the risk to zero.

A spayed cat may still develop mammary cancer because:

• She was spayed after several heat cycles

• Malignant cellular changes had already begun

• Hormonal exposure is not the only factor involved

• Mammary carcinoma can arise despite low recognised risk

Do not assume a mammary lump is benign simply because the cat was spayed.

What Else Can Cause a Mammary Lump?

Not every mammary swelling is cancer.

Important differential diagnoses include:

Fibroadenomatous mammary hyperplasia

This is a rapid, hormone-driven enlargement of one or several mammary glands.

It is most commonly seen in:

• Young entire females

• Pregnant cats

• Cats recently in heat

• Cats exposed to progestogen medication

• Occasionally neutered males or females after hormonal treatment

The glands may become dramatically enlarged over days or weeks. Although the condition is benign, severe swelling can cause pain, skin ulceration and tissue necrosis.

Mastitis or mammary abscess

Infection is most commonly associated with pregnancy or nursing.

Possible signs include:

• Pain

• Heat

• Redness

• Fever

• Abnormal milk or discharge

• Reduced appetite

• Lethargy

• Kittens failing to gain weight

Mastitis can occasionally occur outside lactation, but cancer should remain a consideration in an older cat with an inflamed mammary gland.

Benign mammary tumour

Adenomas and other benign lesions occur, but they are much less common than malignant mammary tumours in cats.

Skin or subcutaneous mass

A lump near the mammary chain may originate from:

• Skin

• Fat

• A cyst

• An enlarged lymph node

• A mast cell tumour

• A soft-tissue sarcoma

• An injection site

• An abscess

The location alone cannot confirm that a mass began within the mammary gland.

Inguinal hernia

A soft or reducible swelling near the groin may represent abdominal tissue passing through an inguinal defect rather than a mammary tumour.

The safest practical rule remains: every new mammary-region lump deserves examination and diagnosis.

How Are Mammary Tumours Diagnosed?

Diagnosis involves answering three different questions:

1. What is the mass?

2. How far has it spread?

3. Is the cat healthy enough for treatment?

1. Complete Examination and Tumour Mapping

The veterinarian should examine both mammary chains, not just the lump the owner noticed.

Each mass should be documented for:

• Exact gland location

• Length, width and depth

• Mobility

• Skin involvement

• Fixation to deeper tissue

• Ulceration

• Nipple involvement

• Number of masses

• Relationship with nearby lymph nodes

The axillary and inguinal lymph nodes should also be assessed.

Photographs and measurements create a useful baseline, particularly when surgery cannot be performed immediately.

2. Fine-Needle Aspiration or Core Biopsy

Fine-needle aspiration may help distinguish a mammary carcinoma from inflammation, a cyst or another type of tumour.

A 2024 study comparing fine-needle aspiration with core needle biopsy reported diagnostic accuracy between approximately 90% and 97.7% for feline mammary tumours. However, cytology cannot provide all the information available from the complete surgically removed tumour.

Histopathology remains essential for assessing:

• Exact tumour type

• Invasion

• Histological grade

• Mitotic activity

• Lymphovascular invasion

• Surgical margins

• Involvement of regional lymph nodes

A cytology result suggesting carcinoma should usually accelerate staging and surgical planning rather than delay treatment while the tumour continues growing.

3. Blood and Urine Testing

Preoperative assessment commonly includes:

• Complete blood count

• Serum biochemistry

• Electrolytes

• Urinalysis

• Blood pressure when indicated

• FeLV and FIV testing according to history and clinical circumstances

These tests do not diagnose mammary cancer. They assess anaesthetic risk, kidney and liver function, anaemia, infection and concurrent disease.

Because most affected cats are seniors, chronic kidney disease, hyperthyroidism, heart disease and other age-related conditions may influence the treatment plan.

4. Chest Imaging

Feline mammary carcinoma frequently spreads to the lungs, pleura and intrathoracic lymph nodes.

Three-view thoracic radiographs are a standard staging test. Thoracic CT is more sensitive and can identify smaller pulmonary nodules and lymph node abnormalities that may not be visible on radiographs.

In a preliminary study involving cats with mammary carcinoma, CT detected more affected cats and more pulmonary nodules than radiography. The smallest nodule seen on CT was approximately 1 mm, compared with 2.5 mm on radiographs.

A normal chest study does not guarantee that microscopic metastasis is absent. It means no detectable thoracic metastasis was identified with that test at that time.

5. Regional Lymph Node Sampling

The relevant regional lymph node should be sampled even when it is not obviously enlarged if the result could affect staging or treatment.

Current oncology guidance recommends regional lymph node aspiration for feline mammary cancer, including normal-sized nodes, because palpation alone cannot reliably exclude microscopic metastasis.

Lymphatic drainage generally follows this pattern:

• Cranial glands drain towards the axillary nodes

• Caudal glands drain towards the inguinal nodes

• The middle glands can have more variable drainage

The superficial inguinal lymph node may be removed with the caudal mammary chain. The axillary node generally requires separate assessment or removal.

6. Abdominal Imaging

Abdominal ultrasound may be recommended to assess:

• Liver

• Spleen

• Abdominal lymph nodes

• Kidneys

• Other age-related disease

• Possible distant metastasis

CT may provide more detailed staging when advanced disease is suspected or major oncological surgery is being planned.

Not every cat requires every possible scan. Testing should be selected according to whether the result would change prognosis, surgery or treatment.

What Information Should the Pathology Report Include?

A useful pathology report should address:

• Histological diagnosis

• Tumour subtype

• Histological grade

• Mitotic count

• Lymphovascular invasion

• Surgical margins

• Skin or muscle invasion

• Necrosis

• Regional lymph node status

• Size of the largest invasive tumour

Histological grade is not decorative terminology. Higher-grade feline mammary carcinomas are associated with more aggressive behaviour and shorter survival. Lymphovascular invasion and lymph node metastasis are also major negative prognostic findings.

Ask for a complete copy of the pathology report rather than accepting only “malignant mammary tumour” as the final description.

How Is Mammary Cancer Staged?

Staging considers three core factors:

• Tumour: size and local invasion

• Nodes: regional lymph node involvement

• Metastasis: distant spread, particularly to the chest

A small tumour with no lymphovascular invasion, no lymph node involvement and no distant metastasis is biologically very different from a large ulcerated tumour with nodal or pulmonary spread.

One large study of 395 cats combined tumour size, lymphovascular invasion and lymph node status into a histological staging system. Increasing stage was associated with shorter disease-free and cancer-specific survival.

The real value of staging is not giving the cancer a Roman numeral. It is deciding whether surgery is likely to provide meaningful local control and whether systemic treatment should be discussed.

What Is the Best Treatment for Mammary Tumours in Cats?

For a resectable tumour without prohibitive metastatic disease, surgery is the central treatment.

The aim is to remove:

• The known tumour

• Mammary tissue at risk of microscopic disease

• Appropriate margins

• Relevant regional lymph nodes where indicated

Feline mammary surgery is usually more extensive than removing only the visible lump.

Why Is Lumpectomy Usually Not Enough?

A lumpectomy removes the obvious mass while leaving most of the surrounding mammary tissue in place.

This is often inadequate because:

• Microscopic tumour may extend beyond the palpable lump

• More than one tumour may already be present

• New tumours may develop elsewhere in the chain

• Cutting too close to the tumour increases the risk of incomplete margins

• Local recurrence can make later surgery more difficult

The first oncological surgery usually provides the best opportunity for complete removal. Unplanned or incomplete surgery can distort normal tissue planes and complicate the definitive procedure.

What Is a Radical Mastectomy?

A radical mastectomy removes an entire mammary chain from the chest to the groin.

Depending on the tumour distribution, the surgeon may recommend:

• Unilateral radical mastectomy

• Staged bilateral radical mastectomy

• Removal of the relevant lymph nodes

• Removal of underlying fascia or muscle when invaded

Current AAHA oncology guidance lists unilateral radical mastectomy with regional lymph node removal, or staged bilateral radical mastectomy, as the main surgical approaches for feline mammary cancer. Simultaneous bilateral radical mastectomy is generally not recommended because of wound tension and postoperative morbidity.

Should Both Mammary Chains Be Removed?

Not every cat automatically requires bilateral surgery, but it deserves serious consideration.

A multicentre study of 107 cats found that bilateral mastectomy was associated with a longer median progression-free survival than unilateral mastectomy:

• Bilateral mastectomy: 542 days

• Unilateral mastectomy: 289 days

Bilateral surgery caused more postoperative complications, supporting the use of staged procedures rather than removing both chains in one operation.

The decision should consider:

• Whether both chains contain tumours

• Number and location of lesions

• Skin availability

• Tumour stage

• Lymph node findings

• Cat’s age and general health

• Anaesthetic risk

• Whether metastatic disease is present

• Owner’s goals and ability to manage two recoveries

When staged bilateral surgery is selected, the second side is commonly removed after the first incision has healed, often around three to five weeks later.

What Happens During Surgery?

A typical procedure involves:

1. Clipping and preparing a large area of the chest and abdomen.

2. Removing the mammary chain as one intact specimen.

3. Avoiding cutting directly through the tumour.

4. Removing regional lymphatic tissue when appropriate.

5. Taking additional deep tissue when the tumour is fixed.

6. Closing the resulting long incision with careful tension management.

7. Submitting all removed tissue and lymph nodes for histopathology.

A surgical drain may be required when there is substantial dead space, although not every cat needs one.

What Is Recovery Like After Mastectomy?

The incision can extend from the chest to the groin and often looks dramatic.

Cats generally need:

• Strong pain relief

• An Elizabethan collar or recovery suit

• Restricted jumping and activity

• Daily wound checks

• Medication as prescribed

• Monitoring of appetite and hydration

• A postoperative examination

• Suture removal when non-absorbable sutures are used

Possible complications include:

• Bruising

• Swelling

• Seroma formation

• Fluid discharge

• Wound infection

• Skin-edge necrosis

• Incision breakdown

• Reduced appetite

• Pain

• Delayed healing

Contact the surgeon promptly if the incision opens, becomes increasingly swollen, produces foul discharge or appears significantly more painful.

A 2021 multicentre study of cats undergoing bilateral mastectomy found postoperative complications in both staged and single-session procedures. Incomplete excision and later local recurrence were associated with poorer outcomes.

Should an Entire Cat Be Spayed During Mammary Surgery?

Spaying is strongly protective when performed early in life, but it does not treat or remove an established mammary cancer.

For an entire cat already diagnosed with a tumour, ovariohysterectomy may still be discussed because it:

• Prevents future pregnancy

• Prevents pyometra

• Stops future heat cycles

• Removes ovarian and uterine disease risk

• Eliminates further endogenous reproductive cycling

Whether it is performed during the same anaesthetic depends on the cat’s stability, expected surgical duration and the oncological plan.

Spaying should never delay removal of a malignant mammary tumour while an owner waits for the “right time” in the cat’s cycle.

Does Chemotherapy Improve Survival?

The evidence is mixed.

Chemotherapy is commonly discussed for cats with higher-risk features such as:

• Large tumour size

• High histological grade

• Lymphovascular invasion

• Lymph node metastasis

• Incomplete margins

• Local recurrence

• Multiple invasive tumours

• Distant metastasis

Doxorubicin has historically been one of the most frequently used drugs. Other protocols may include carboplatin, cyclophosphamide, metronomic treatment or targeted medication.

However, no chemotherapy protocol has been consistently proven to improve survival for every cat following mammary surgery.

One retrospective study found no clear benefit from adjuvant doxorubicin compared with surgery alone. Another multicentre analysis comparing surgery alone, surgery plus doxorubicin and surgery plus metronomic cyclophosphamide with meloxicam also found no significant survival difference between the groups.

Conversely, the 2018 surgical study found an association between chemotherapy and a reduced risk of cancer-specific death. Because the available studies are retrospective and involve different tumour stages and protocols, selection bias makes firm conclusions difficult.

The practical conclusion is:

Chemotherapy is not an automatic requirement for every small, completely removed mammary carcinoma, but it should be discussed with an oncologist when the pathology or stage indicates substantial metastatic risk.

What About Toceranib and Targeted Treatment?

Toceranib is a tyrosine kinase inhibitor used extra-label in cats.

A small 2024 study of cats with advanced feline mammary carcinoma reported a median progression-free survival of 91 days and median overall survival of 145 days. This suggests potential biological activity, but the study was small and does not establish toceranib as a curative or standard first-line treatment.

Potential adverse effects include:

• Reduced appetite

• Vomiting

• Diarrhoea

• Weight loss

• Bone marrow suppression

• Proteinuria

• Blood pressure changes

• Kidney or liver abnormalities

Targeted medication should be selected and monitored by a veterinary oncologist.

Is Radiation Therapy Used?

Radiation therapy is not routinely the primary treatment for most resectable feline mammary tumours.

It may be considered when:

• Surgical margins are incomplete

• The tumour cannot be fully removed

• Local recurrence develops

• Surgery would cause unacceptable morbidity

• Palliation of pain or a local mass is needed

The evidence is much more limited than it is for surgery. Referral to a radiation oncologist is needed to determine whether the expected benefit justifies repeated anaesthesia and treatment.

Can Surgery Still Be Performed If Cancer Has Spread?

Sometimes, but the goal changes.

Removing the primary tumour may still be considered when it is:

• Ulcerated

• Bleeding

• Infected

• Painful

• Interfering with movement

• Creating a major daily welfare problem

This is palliative surgery rather than curative treatment.

The benefit must be weighed against:

• Anaesthetic risk

• Surgical recovery

• Expected metastatic progression

• Current breathing and appetite

• Whether the wound is likely to heal

• The amount of comfortable time surgery is expected to provide

A large operation is not automatically kind merely because the tumour can technically be removed.

What Does Palliative Care Involve?

Palliative care focuses on comfort when cure or meaningful long-term control is not achievable.

It may include:

• Pain relief

• Anti-inflammatory medication when medically appropriate

• Treatment of nausea

• Appetite support

• Wound cleaning

• Non-stick dressings

• Antibiotics for confirmed or strongly suspected secondary infection

• Preventing licking

• Nutritional support

• Drainage of pleural fluid when present

• Oxygen support

• Targeted chemotherapy or toceranib in selected cats

• Quality-of-life monitoring

• Planned euthanasia before an uncontrolled crisis develops

Antibiotics may reduce infection and odour from an ulcerated tumour, but they do not shrink or treat the cancer.

Human pain medication must never be given unless specifically prescribed. Paracetamol is highly toxic to cats, and ibuprofen, naproxen and several other human anti-inflammatory drugs can cause severe or fatal injury.

What Is the Prognosis?

The prognosis depends on the interaction of several factors.

The most important include:

• Tumour size

• Lymph node involvement

• Lymphovascular invasion

• Histological grade

• Completeness of surgical margins

• Local recurrence

• Distant metastasis

• Ulceration

• Number of tumours

• Overall health of the cat

Tumour size is important, but it should not be interpreted alone.

A 1.5 cm tumour with lymphovascular invasion and a positive lymph node may behave more aggressively than a slightly larger tumour without either finding.

How Does Stage Affect Survival?

In a study of 395 surgically treated cats, a histological staging system based on tumour size, lymphovascular invasion and lymph node status produced the following median cancer-specific survival times:

Histological pattern	Median cancer-specific survival
Carcinoma in situ	1,484 days
Tumour 2 cm or smaller, without lymphovascular invasion or nodal metastasis	808 days
Tumour larger than 2 cm, without lymphovascular invasion or nodal metastasis	377 days
Tumour 2 cm or smaller with lymphovascular invasion or nodal metastasis	448 days
Tumour larger than 2 cm with lymphovascular invasion or nodal metastasis	207 days

These are group medians, not expiry dates. Individual cats may live for much shorter or considerably longer periods.

Current AAHA guidance summarises the broader evidence as follows:

• Tumours smaller than 2 cm may have median survival measured in years

• Tumours larger than 3 cm often have median survival measured in months

• Chemotherapy benefit remains uncertain

• Node, liver and lung metastasis significantly worsen prognosis

This is why “come back if it gets bigger” is particularly poor advice for a feline mammary lump.

What Is the Prognosis After Metastasis?

Distant metastatic disease carries a poor prognosis, although selected cats remain comfortable for meaningful periods.

In a multicentre study of 73 cats with stage IV mammary cancer:

• Overall tumour-specific survival was very short

• Cats already showing clinical signs from metastasis had a worse outcome than asymptomatic cats

• Pleural effusion was associated with particularly short survival

• No chemotherapy group demonstrated a clear survival advantage

• A small number of cats survived longer than six months

The study population had confirmed advanced disease, so its figures should not be applied to a cat with a newly detected small local tumour.

When Is a Mammary Tumour an Emergency?

Go to an emergency veterinary hospital immediately if your cat develops:

• Open-mouth breathing

• Marked breathing effort

• Blue, grey or extremely pale gums

• Collapse

• Inability to stand

• Uncontrolled tumour bleeding

• Severe distress

• Reduced consciousness

• Rapidly worsening chest or abdominal swelling

Arrange same-day veterinary care if your cat has:

• An ulcerated tumour producing discharge

• Rapid tumour enlargement

• Significant pain

• Refusal of food

• Fever or profound lethargy

• Foul odour and surrounding inflammation

• Persistent bleeding

• Swelling of a leg

• A surgical incision that has opened

• Breathing that is persistently faster than normal at rest

An ulcerated mammary tumour is not merely unpleasant to look at. It can cause pain, blood loss, infection and substantial deterioration in quality of life.

What Should You Do Next?

1. Check the Entire Mammary Chain

Gently feel from the chest to the groin on both sides.

Record:

• Number of lumps

• Exact location

• Approximate size

• Whether the lump moves

• Any redness, discharge or ulceration

Do not repeatedly squeeze, massage or attempt to drain the mass.

2. Arrange an Examination Within Days

Do not wait several months to see whether it grows.

A small lump that turns out to be benign has lost little by being assessed early. A small malignant lump may lose its best treatment window if investigation is delayed.

3. Obtain Staging Before Major Surgery

Discuss:

• Blood and urine testing

• Three-view chest radiographs or thoracic CT

• Regional lymph node sampling

• Abdominal imaging

• Surgical approach

• Referral to a surgical oncologist

4. Plan the First Surgery Properly

Ask whether the recommended procedure is:

• Local excision

• Unilateral radical mastectomy

• Staged bilateral mastectomy

• Lymph node removal

• Removal of underlying fascia or muscle

Ask why that approach is appropriate for this particular tumour distribution.

5. Submit Every Mass and Lymph Node

Do not discard tissue without histopathology.

When several masses are present, each should be identified and submitted so the pathologist can determine whether they have the same diagnosis and grade.

6. Review the Full Pathology Report

Discuss:

• Margins

• Grade

• Lymphovascular invasion

• Lymph node status

• Tumour subtype

• Need for further surgery

• Need for oncology consultation

7. Create a Monitoring Plan

High-grade cancers are generally reassessed more frequently than low-grade tumours.

Current oncology guidance recommends tailoring follow-up to grade, stage and treatment. High-grade tumours may need examinations every one to three months, while lower-grade tumours may be reviewed every four to six months. Monitoring can include examination of both mammary chains, lymph node assessment, chest imaging and blood testing when indicated.

Common Mistakes Owners Should Avoid

Waiting for the lump to become large

Tumour size strongly affects treatment options and prognosis.

Assuming a small lump cannot be cancer

Many feline mammary carcinomas begin as very small, painless nodules.

Removing only the visible lump without oncological planning

An unplanned lumpectomy may leave microscopic disease and complicate later surgery.

Skipping chest staging because the cat breathes normally

Pulmonary metastases may be present before obvious respiratory signs develop.

Ignoring normal-sized lymph nodes

Microscopic metastasis can occur without visible lymph node enlargement.

Treating an ulcerated tumour repeatedly with antibiotics

Antibiotics may improve secondary infection without treating the cancer.

Assuming spaying now will make the tumour disappear

Spaying is preventive when performed early. It is not a substitute for tumour removal.

Believing chemotherapy definitely improves survival

Chemotherapy may be appropriate in high-risk cases, but the overall feline evidence remains mixed.

Treating a survival estimate as a deadline

Median survival figures describe groups, not the individual cat sitting in front of you.

Can Mammary Tumours Be Prevented?

Not every mammary tumour can be prevented, but risk can be reduced substantially.

Spay female cats early

The strongest protective effect occurs when cats are spayed before six months to one year of age. AAHA endorses sterilising female cats by approximately five months, before many experience their first heat.

Avoid unnecessary progestogen exposure

Do not use hormonal heat-suppression products without a clear veterinary indication and discussion of risks.

Check the mammary chain regularly

Once a month, gently feel along both mammary chains.

This is especially important for:

• Entire females

• Cats spayed after their first year

• Cats previously given hormonal medication

• Senior cats

• Siamese or related breeds

• Cats with a previous mammary tumour

Include the mammary glands in senior examinations

A complete senior examination should include palpation of all eight glands and regional lymph nodes.

Earlier detection does not guarantee cure, but it provides the best chance of removing the tumour before it has become large, invasive or metastatic.

Frequently Asked Questions

Is every mammary lump in a cat cancer?

No, but approximately 80% to 90% of feline mammary tumours are malignant. Every mammary lump should therefore be investigated promptly rather than monitored casually.

How fast do feline mammary tumours grow?

Growth varies. Some remain small for weeks or months, while high-grade or inflammatory tumours can enlarge rapidly. The absence of obvious growth over a short period does not prove that a lump is benign.

Should the entire mammary chain be removed?

Chain-based mastectomy is commonly recommended because local excision alone may leave microscopic or multifocal disease. Whether one or both chains should be removed depends on tumour distribution, staging and the cat’s ability to tolerate surgery.

Can a cat live for years after mammary cancer surgery?

Yes. Cats with small, completely removed tumours and no lymphovascular, lymph node or distant spread may survive for years. Large tumours, positive nodes, high grade, incomplete margins and metastasis substantially worsen the outlook.

Can mammary cancer occur in a male cat?

Yes. It is rare but often aggressive, and a mammary mass in a male cat requires the same prompt investigation as one in a female cat.

Final Takeaway

Mammary tumours in cats are common enough to recognise and aggressive enough that early action genuinely changes the outcome.

Most feline mammary masses are malignant. The strongest treatment opportunity is usually when the tumour is still small, removable and has not spread to the lymph nodes or chest.

The correct approach is not simply to remove the lump. It is to:

• Examine and measure every mammary gland

• Stage the chest and regional lymph nodes

• Plan the first surgery properly

• Submit the complete tissue for histopathology

• Use grade, margins, lymphovascular invasion and stage to guide further treatment

• Monitor closely for recurrence and metastasis

A pea-sized lump deserves attention now, not when it has become an ulcerated mass several centimetres across.

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If you have found a mammary lump, are trying to understand a pathology report or are unsure whether your cat’s breathing, bleeding or appetite change is urgent, ASK A VET™ can help you organise the information and prepare the right questions for your veterinarian.