Mastectomy: Causes, Diagnosis, and When to Consider Surgery

Medically reviewed by the Know Your Surgery Editorial Team. Last reviewed: May 2026.

Mastectomy is recommended when breast cancer cannot be safely or effectively treated with breast-conserving surgery, when there is a strong genetic risk that warrants prevention, or when patient preferences and clinical factors favor mastectomy over lumpectomy. This article explains what contributes to breast cancer risk, how clinicians make the diagnosis, and how the decision to proceed with mastectomy is made. If you are new to the topic, the cluster overview article is a useful starting place.

What Causes Breast Cancer?

The exact cause of any individual breast cancer is rarely known. Cancer develops when cells in the breast accumulate genetic changes that allow them to grow out of normal control. Several factors raise the likelihood of developing breast cancer.

Female sex. Breast cancer is far more common in women than men, although men can also develop it.

Age. Risk rises significantly after age 50.

Family history. Having a close relative with breast or ovarian cancer increases risk, especially if the relative was diagnosed at a young age.

Inherited genetic mutations. Mutations in BRCA1, BRCA2, PALB2, and several other genes greatly raise lifetime breast cancer risk. Genetic counseling and testing are recommended for patients with strong family history.

Personal history. A previous breast cancer or certain non-cancerous breast biopsies (such as atypical ductal hyperplasia) raise risk.

Reproductive factors. Early first menstrual period, late menopause, never having been pregnant, or first pregnancy after age 30 modestly raise risk.

Hormonal factors. Long-term combined hormone replacement therapy after menopause raises risk.

Lifestyle factors. Alcohol use, obesity (especially after menopause), and physical inactivity modestly raise risk.

Radiation exposure. Radiation to the chest at a young age (for other cancer treatment) raises risk.

Many breast cancers occur in women without obvious risk factors. Most breast lumps are not cancer.

Risk Factors That Increase the Likelihood of Mastectomy

Mastectomy is generally needed (rather than lumpectomy) when:

• The tumor is large relative to the breast size
• Cancer is found in multiple areas of the same breast (multifocal or multicentric)
• The patient has an inherited mutation that raises future cancer risk
• The patient cannot have radiation (for example, has had prior chest radiation)
• The cancer recurred after lumpectomy and radiation
• The patient prefers mastectomy after careful discussion

These factors do not predict mastectomy on their own; the choice is shared with the patient.

Symptoms Suggesting Breast Cancer

Many early breast cancers cause no symptoms and are found by screening mammogram. When symptoms appear, common signs include:

• A new lump or mass in the breast or underarm
• Thickening or swelling of part of the breast
• Skin changes (dimpling, puckering, redness, scaling)
• Nipple changes (inversion, scaling, persistent rash)
• Nipple discharge that is new, persistent, or bloody
• Pain in one specific area that does not resolve
• Change in breast size or shape

Severe symptoms that require prompt evaluation:

• A rapidly enlarging mass
• Skin redness with warmth (could suggest inflammatory breast cancer or infection)
• Persistent breast pain with skin changes
• A lump that is hard, fixed, or growing

Anyone with persistent or new breast changes deserves clinical evaluation. Self-exams and screening mammograms are key tools for early detection.

How Clinicians Diagnose Breast Cancer

When a breast change is suspected, the team typically follows a structured evaluation.

Detailed history. The clinician asks about the timing of symptoms, family history, prior breast biopsies, hormonal factors, and overall health.

Clinical breast exam. The clinician examines both breasts, the chest wall, and the underarm and neck lymph nodes.

Imaging studies. The choice depends on age, density of breast tissue, and symptoms.

• Diagnostic mammogram is the first imaging test for most adult women with a breast change.
• Breast ultrasound helps characterize masses and is often used along with mammogram.
• Breast MRI is used in select cases (high-risk screening, dense breasts, or unclear findings).
• Tomosynthesis (3D mammogram) is used at many centers for both screening and diagnostic imaging.

Biopsy. A tissue sample is essential to confirm cancer and identify the type. Most breast biopsies are done with a needle in the radiology suite (core needle biopsy), often with imaging guidance. The pathology report describes the cancer type, grade, hormone receptor status (ER, PR), HER2 status, and additional markers.

Genetic testing. Patients with strong family history, certain ages at diagnosis, or specific cancer types are often offered genetic counseling and testing.

Staging studies. For invasive cancer, additional tests (CT scan, bone scan, PET scan, blood tests) help determine the stage. Staging guides decisions about surgery, chemotherapy, radiation, and hormonal therapy.

Differential Diagnosis

Several conditions can cause breast changes that resemble cancer.

• Benign breast cysts
• Fibroadenomas
• Fat necrosis
• Mastitis (infection)
• Ductal papillomas
• Lipomas
• Hormonal changes (cyclic breast pain or fullness)

The diagnostic workup helps the team distinguish these from cancer. Most breast lumps are not cancer.

Mastectomy vs Lumpectomy

For many women with early-stage breast cancer, lumpectomy (removing the cancer with a margin of normal tissue) followed by radiation has similar long-term survival outcomes to mastectomy. The choice depends on:

Tumor size and location. Smaller, single-area cancers in adequate-size breasts are often candidates for lumpectomy.

Multiple areas of cancer. Multifocal or multicentric cancers usually require mastectomy.

Margin status. If lumpectomy cannot remove the cancer with clean margins, mastectomy may be needed.

Radiation eligibility. Patients who cannot receive radiation may need mastectomy.

Genetic risk. Patients with BRCA1/BRCA2 or other high-risk mutations often choose bilateral mastectomy.

Patient preferences. Some women prefer mastectomy for peace of mind, ease of follow-up, or other personal reasons.

The decision is shared with the patient after a detailed discussion of options, expected outcomes, and reconstruction.

When to Consider a Mastectomy

A mastectomy is generally considered when:

• Lumpectomy cannot achieve clean margins
• Cancer is in multiple areas of the breast
• The patient cannot or does not want radiation
• Cancer has recurred after prior breast-conserving surgery
• The patient has high-risk genetic mutations
• The patient prefers mastectomy after careful counseling
• Inflammatory breast cancer is diagnosed
• A large tumor relative to breast size makes lumpectomy cosmetically unsatisfactory

Decisions are made in conversation with the breast surgery, plastic surgery, medical oncology, and (sometimes) genetics teams.

How the Decision Is Made

The choice depends on several factors:

Cancer characteristics. Type, size, location, grade, hormone receptor and HER2 status, and stage.

Patient anatomy. Breast size, tumor-to-breast ratio, and chest wall anatomy.

Patient health. Heart, lung, kidney, and other conditions affecting anesthesia and healing.

Patient values. Some patients prioritize breast preservation; others prioritize mastectomy. Both choices can be the right answer for different people.

Reconstruction goals. If reconstruction is desired, the plastic surgeon’s input shapes the surgical plan.

Future surveillance. Mastectomy reduces but does not eliminate future cancer risk. Patients who keep breast tissue need ongoing screening.

Pre-Surgical Preparation

When mastectomy is planned, the team typically prepares the patient:

• Pre-operative blood tests
• Anesthesia consultation
• Imaging review with the surgical team
• Conversation with the plastic surgeon if reconstruction is planned
• Counseling and support resources for emotional preparation
• Genetic counseling if a mutation is identified
• Medication review, especially blood thinners and hormonal medications
• Detailed informed consent discussion

Detailed coverage of the procedure itself lives in our procedure and recovery article.

Conditions That May Affect the Surgical Plan

Some coexisting conditions can change how mastectomy is performed:

• Heart, lung, or kidney disease. Anesthesia and recovery plans are tailored.
• Diabetes. Healing is monitored more closely.
• Smoking. Strongly discouraged; smoking impairs wound healing and reconstruction.
• Bleeding disorders or anticoagulant therapy. May require pausing certain medications.
• Prior chest radiation. Affects reconstruction options.
• Previous breast surgery. May change the technique.
• Pregnancy. Surgery may be deferred or adjusted.

The team accounts for these factors when planning surgery.

What Happens After You Decide

Once mastectomy is scheduled, the surgical and (if applicable) reconstruction teams prepare the patient. The surgery itself, the recovery in the hospital, and the home recovery period are covered in detail in our procedure and recovery article.

The conversation with your surgical team is detailed but important. Key things to confirm: type of mastectomy, lymph node plan, reconstruction plan, expected hospital stay, drain management, follow-up schedule, and emergency contact for after surgery.

Continue Reading the Mastectomy Cluster

• Mastectomy: Overview, Types, and What to Expect
• Mastectomy: Procedure, Recovery, and Rehabilitation
• Mastectomy: FAQs, Statistics, and Patient Stories

Sources

• American Cancer Society (ACS). Breast cancer: causes and diagnosis. https://www.cancer.org/cancer/types/breast-cancer.html
• National Cancer Institute (NCI). Breast cancer treatment. https://www.cancer.gov/types/breast/patient/breast-treatment-pdq
• Centers for Disease Control and Prevention (CDC). Breast cancer statistics. https://www.cdc.gov/breast-cancer/
• Mayo Clinic. Mastectomy: who needs it. https://www.mayoclinic.org/tests-procedures/mastectomy/about/pac-20384879
• Cleveland Clinic. Mastectomy: causes and decisions. https://my.clevelandclinic.org/health/treatments/8330-mastectomy
• American Society of Clinical Oncology (ASCO). Breast cancer guidelines. https://www.asco.org/practice-patients/guidelines

Medical Disclaimer

The information in this article is for general education and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about breast cancer diagnosis, screening, or surgery.