Found a lump in my breast? Is it cancerous? — Self-Check Guide by a specialist doctor.

ป้าหมอนุช
6 hours ago
10 min read

When you find a lump in your breast, the most important thing is not to panic, but also not to delay treatment. Approximately 80-90% of breast lumps are not cancerous; they could be fibrodenomas, cysts, or hormonal changes. However, a diagnosis cannot be made by palpation alone. Every lump must be evaluated by a specialist using a Triple Assessment process (Physical Exam + Imaging + Biopsy). Suspicious lumps include those that are hard, have irregular edges, are attached to the skin or muscle, are rapidly growing, have dimpling, or have fluid/blood discharge from the nipple or enlarged axillary lymph nodes. You should see a breast specialist as soon as possible.

How common are breast lumps?

Breast lumps are a very common problem in women of all ages — statistics from the American Cancer Society report that approximately 50% of women will experience a lump or change in their breast at some point in their lifetime, and most are not cancerous.

Important information that women should know:

80-90% of breast lumps are not cancerous — most are fibrodenomas, cysts, or fibrocystic changes.
One in 16 Thai women has a chance of developing breast cancer at some point in their lifetime (National Cancer Institute).
Early detection results in a 5-year survival rate of >95% for early-stage breast cancer.
Lumps in women under 30 are mostly fibroids — but not all.
Lumps in women over 50 years old require more thorough examination because the risk of cancer is higher.

Likely benign lumps

Breast lumps with the following characteristics are usually not cancerous, but still need to be confirmed by a doctor.

Smooth, circular/oval edges — Well-circumscribed margins
Easily movable (Mobile) — Does not stick to the skin or muscles.
Smooth, soft, or flexible surface — like an eraser, not hard as a rock.
Size is fixed or changes with the menstrual cycle.
It might be slightly painful — especially before or during your period.
There may be multiple nodules on both sides — they are fibrocystic.

Suspicious lumps/lumps — 9 Warning Signs

Breast lumps with the following characteristics have a higher chance of being cancerous and should be examined by a doctor as soon as possible.

1. Hard, rock-like.

Cancerous tumors are often more hard and rock-like than benign tumors — due to the desmoplastic reaction in which cancer cells trigger stromal fibrosis.

2. Irregular/Spiculated Margins

Cancerous tumors often have indistinct, spiculated borders, unlike fibrodenomas which have smooth, circular borders.

3. Fixed — Attached to the skin or muscle.

A lump attached to the skin or muscle beneath the breast (tested by having the patient contract their chest muscles) indicates that the cancer may have invaded surrounding structures.

4. Rapid scaling.

Rapidly growing lumps, which can develop within weeks to months, differ from benign lumps that typically grow slowly or remain stagnant.

5. Changes in breast skin.

Skin Dimpling
Orange peel-like skin (Peau d'orange) — A sign of inflammatory breast cancer.
The skin on the breast is red and inflamed.
The skin becomes abnormally thickened.

6. Nipple changes.

Newly developed nipple inversion.
Nipple tilted to one side.
Rash/sores on the nipple — may be Paget's Disease.
Lymphatic fluid/blood coming from the nipple, especially on only one side.

7. Enlarged lymph nodes in the armpit.

Axillary lymph nodes that are palpable, hard, or attached to the skin/muscle indicate cancer spread to the lymph nodes.

8. Only one lump.

Benign nodules are often found on both sides (e.g., fibrocystic), while cancerous nodules are usually found on one side and in a fixed location.

9. Painless.

Surprisingly, most breast cancer lumps are painless — while benign lumps like cysts or fibrodenomas may be painful — so the absence of pain doesn't mean it's safe.

Causes of non-cancerous breast lumps.

Fibroadenoma — a benign tumor.

Most common in women aged 15-35 years. • A firm, smooth, easily movable mass. • 1-3 cm in size. • Non-cancerous. • Sometimes shrinks on its own after menopause. • Most do not require surgery unless they grow rapidly or the patient is anxious.

Cyst — fluid-filled sac

Common in women aged 35-50 years. It's a breast cyst (fluid-filled sac) that is soft or flexible, changes size with the menstrual cycle, and is diagnosed with ultrasound. If larger than 3 cm, the fluid may be aspirated.

Fibrocystic Changes — Hormonal Changes

Found in 50% of women of reproductive age. Symptoms include multiple lumps on both sides, breast pain before menstruation, and are not a disease but a natural change.

Mastitis — Inflammation of the breast

Common in breastfeeding women: Redness, swelling, warmth, and tenderness of the breast; fever; requires antibiotic treatment. ⚠️ Caution: If symptoms do not improve within 1-2 weeks, further testing is needed to rule out inflammatory breast cancer.

Fat necrosis — Localized death of adipose tissue.

Caused by injury, surgery, or radiation therapy; a cancer-like mass on a mammogram; requires a biopsy to rule it out as cancer.

Phyllodes Tumor — A special type of tumor.

Common in women aged 40-50 years. Hard, rapidly growing lump. 85% are benign, but 15% may be malignant. Surgery is required in all cases.

Intraductal Papilloma

Small mass in the milk duct · Often causes discharge of lymphatic fluid/blood from the nipple · Has a small risk of developing into DCIS · Requires surgical removal.

Self-Assessment Checklist — Do it yourself in 3 minutes.

This tool helps instructors make an initial risk assessment, but it cannot replace a medical examination.

Characteristics of the lump — Tick ✅ all options that match your condition:

☐ Hard as a rock (not soft, not flexible)
☐ Irregular, jagged, and indistinct edges.
☐ Unable to move; stuck to skin or muscle.
☐ Rapid size increase over the past 1-3 months.
☐ Found on only one side.
☐ It doesn't hurt.
☐ Larger than 2 cm.

Associated symptoms — Tick ✅ all that apply:

☐ Changes in breast skin (dimples, orange peel texture, redness)
☐ Inverted nipples (recently occurred).
☐ There is fluid/blood coming out of the nipple.
☐ Lymph nodes can be felt in the armpit.
☐ Family history of breast/ovarian cancer.
☐ Age > 40 years
☐ Never had a mammogram screening.

Interpret the scores:

0-2 points: Low risk — but you should still consult a doctor for confirmation.
3-5 points: Moderate risk — See a doctor within 1-2 weeks.
6+ signs: High risk — See a breast specialist as soon as possible.

⚠️ Important: This checklist is a preliminary screening tool and cannot replace a medical diagnosis — even a low score should be confirmed by a doctor using the Triple Assessment.

Diagnosis — Triple Assessment Standard

The international standard for breast lump assessment is the Triple Assessment — a simultaneous evaluation of three components for maximum accuracy (Sensitivity > 99%).

1. Clinical Examination (Physical examination by a physician)

Examine and palpate both breasts in both sitting and lying positions.
Examine the nipples — for indentations, sores, rashes, or fluid.
Check the lymph nodes in the armpit and clavicle.
Assess the size, location, and characteristics of the mass.
Assess family history and risk factors.

2. Imaging (Image examination)

Mammogram — Gold Standard

For use in women aged ≥ 40 years. At Namarak, we use Hologic 3D Mammography + Genius AI Detection — high sensitivity 94%. Detects microcalcifications that may be a sign of DCIS.

Ultrasound (US) — Supplementary tool

Used in women under 40 years old with dense breast tissue. Clearly distinguishes solid masses from cysts. Used as a guide for biopsy.

MRI — Special Cases

Used in high-risk patients (BRCA carriers) · Nodules that appear normal on imaging but are clinically suspicious · Assess the extent of the disease.

3. Biopsy (Tissue sample examination)

It is the only step that can confirm whether or not it is cancer.

Core Needle Biopsy (CNB) — Standard · Uses a 14G needle · Guided by ultrasound or mammogram · Non-surgical.
Vacuum-Assisted Biopsy (VAB) — Used for microcalcifications or small lumps.
Excisional Biopsy — Surgical removal of the entire mass. Used when a core needle cannot access the area.
FNA (Fine Needle Aspiration) — Less commonly used today. Used only for cyst aspiration.

BI-RADS — The International Language for Breast Lump Assessment

BI-RADS (Breast Imaging Reporting and Data System), by the American College of Radiology, is a standard system for reporting breast imaging results.

BI-RADS 0: Further examination required — Image is unclear.
BI-RADS 1: Normal (Negative) — 0% cancer risk.
BI-RADS 2: Definitely Benign — 0% cancer risk.
BI-RADS 3: Probably benign — Cancer risk < 2% · Follow-up appointment in 6 months.
BI-RADS 4: Suspicious — 2-95% risk of cancer · Biopsy required.
BI-RADS 4A: Low suspicion (2-10%)
BI-RADS 4B: Moderate suspicion (10-50%)
BI-RADS 4C: High suspicion (50-95%)
BI-RADS 5: Almost certainly cancer — risk > 95% · Biopsy required.
BI-RADS 6: Cancer confirmed via biopsy.

When should you seek immediate medical attention? (Red Flags)

Within 1 week:

A suspicious lump (hard, irregular edges, immobile).
A rapidly growing lump
Lymphatic fluid/blood coming from the nipple (especially on only one side).
Nipple inverted, changes in breast skin.

Within 24-48 hours (Urgent):

Red, swollen, and orange-yellow breasts, especially if not breastfeeding, could be inflammatory breast cancer.
A rash/sore on the nipple that doesn't heal within 2 weeks — may be Paget's Disease.
A hard, enlarged lump in the armpit, attached to the skin/muscle.
The lymph fluid contains fresh blood.

Breast self-examination (BSE) — the correct way

It is recommended to do this once a month. For women of reproductive age, do it 7-10 days after menstruation ends (because the breasts will be softest then). For women in menopause, choose the same day each month.

Step 1: Inspection

Stand in front of a mirror with your hands at your sides, then raise your arms above your head. Observe both positions.

Are the two breasts the same size and shape?
Is the breast skin smooth? Are there any indentations, cellulite, or redness?
Are the nipples in a normal position? Are they indented or tilted?
Is there any fluid/blood on the nipple?

Step 2: Palpation in a standing position.

Use your left hand to examine your right breast and your right hand to examine your left breast. Use your index, middle, and ring fingers (3 fingers total). Apply pressure at three levels: light, medium, and heavy.

Step 3: Palpation in the supine position (Palpation Supine)

Lie supine with a pillow under the shoulder of the side to be examined. Raise that arm above your head. Using three fingers, palpate the breast in a circular motion, covering the area from the collarbone to below the breast and from the sternum to the armpit.

Step 4: Check the armpit.

Palpate the lymph nodes in both armpits. Relax the arm being examined. Use the other hand to palpate.

💡 Tip: A BSE (Breast Self-Examination) helps you become familiar with your breasts, allowing you to notice changes sooner — but a BSE alone isn't enough; mammograms are also necessary as needed.

Breast lump diagnosis at Numarak Hospital.

As a specialized breast disease hospital, we offer a comprehensive breast lump assessment process all under one roof.

Triple Assessment in One Day

Clinical examination by 5 breast surgeons — Fellowship-trained team.
Hologic 3D Mammography + Genius AI Detection — 94% sensitivity (MGH 2025: 32% missed cancers detected by AI)
Ultrasound and MRI — Breast Radiology Specialist Team
Core needle biopsy on the same day — results available in 2-3 days.
Multidisciplinary Tumor Board — Reviews complex cases by a team of expert physicians.

High Tech, High Touch Philosophy

At Numarak Hospital, we believe in the philosophy of "like visiting a friend's house" — world-class technology combined with empathetic care. Our Patient Journey Coordinator team will provide care and guidance throughout the process, reducing anxiety and making breast lump assessment a warm and welcoming experience.

Frequently Asked Questions (FAQ)

Should I see a doctor immediately if I have a small lump about 1 cm in size?

Size of a lump is not the only factor determining whether it's cancerous or not — a 1 cm lump that looks suspicious (hard, irregular edges) is more dangerous than a 3 cm lump that is soft and movable. Every newly discovered lump should be evaluated by a doctor within 1-2 weeks — the earlier it's detected, the better the treatment outcome.

Does a painful lump mean it's not cancerous?

False — While most cancerous lumps are painless, some types, such as inflammatory breast cancer, can be painful. The presence of pain doesn't mean it's safe, and similarly, painlessness doesn't necessarily mean it's cancer — only a Triple Assessment can provide an accurate diagnosis.

Where is the best place to get a breast cancer screening?

Choose a hospital with a breast specialist team, Hologic 3D Mammography technology, AI, the ability to perform core needle biopsy, and a multidisciplinary tumor board for complex cases. Breast specialist hospitals, such as Namarak Hospital, have a high case volume and better outcomes than general hospitals (re-excision rate 8-12% compared to 25-35%).

Can young women (< 25 years old) get breast cancer?

Yes, but it's rare — breast cancer in women under 25 years old accounts for only 0.4% of all breast cancer cases. Most tumors at this age are fibrodenomas, but if there is a family history of breast/ovarian cancer (especially BRCA1/2 mutations), a thorough screening is warranted.

Does a mammogram hurt?

Breast compression may be slightly to moderately painful — it only takes 10-20 seconds per image. Breast compression is necessary to obtain clear images, reduce the radiation dose, and better detect abnormalities — the total duration is approximately 15-30 minutes.

What should I do if my mammogram is normal but a lump is still palpable?

A lump that can be felt but is normal on a mammogram may still require an ultrasound, especially in women with dense breast tissue that may not be visible on a mammogram. If all imaging is normal but the doctor still suspects something is wrong, an MRI or biopsy may be necessary for confirmation. A triple assessment emphasizes comprehensive care, not just one type of test.

I have a lump but I don't want surgery. Is it possible?

Depending on the diagnosis — if the biopsy confirms a small fibrodenoma (< 2 cm) and the patient is not concerned, follow-up may be an option instead of surgery. If it's a cyst, fluid can be drained without surgery. However, if it's cancerous or a suspected mass (BI-RADS 4-5), surgery is necessary for treatment and definitive diagnosis.

Is a breast lump that changes size with your menstrual cycle cancerous?

Typically, lumps that change size with the menstrual cycle (growing larger before menstruation and shrinking after menstruation ends) are a sign of fibrocystic changes or cysts, which are not cancerous — however, self-diagnosis based solely on observation should be avoided. Any newly discovered lump should be examined by a doctor at least once for confirmation.

Consult a breast specialist at Numarak Hospital.

If you find a lump in your breast or have any worrisome symptoms, our medical team can perform a Triple Assessment in a single day. Contact us at:

Tel: 02-059-0245
LINE: @namarak (page.line.me/vfg3683z)
Book an appointment online.
Request a second opinion.
Our medical team

About the editor.

Assoc. Prof. Yaowanuch Kongdan , M.D., Breast Surgeon + Surgical Oncologist · Founder and Director of Namarak Hospital · President of the Thai Breast Disease Society (TBS)

Note: This article is for general information only and cannot replace diagnosis and advice from a specialist. If you have any concerns, you should consult a doctor for a direct evaluation. Finding a lump in the breast does not always mean it is cancerous, and all lumps should be evaluated by a doctor for safety reasons.

References

ACR BI-RADS Atlas 5th Edition — American College of Radiology
NCCN Clinical Practice Guidelines — Breast Cancer Screening and Diagnosis
ACS Breast Cancer Facts & Figures 2025-2026
ASBrS (American Society of Breast Surgeons) — Triple Assessment Guidelines
Thai Breast Disease Society (TBS) — Clinical Practice Guidelines