Breast cancer is the most common cancer affecting women in Singapore, accounting for approximately 29% of all cancers diagnosed in Singaporean women. Roughly 2,100 women are diagnosed with breast cancer in Singapore each year. It is also one of the most treatable cancers in medicine -- when detected early, survival rates exceed 95%. Understanding your breast cancer, its type, subtype, and stage, is the foundation of your treatment conversation with your breast cancer specialist.
Breast Cancer in Singapore
According to the Singapore Cancer Society, 1850 women are diagnosed with breast cancer every year and more than 400 would die from the disease. Advancements in breast cancer screening allow healthcare professionals to diagnose breast cancer earlier. Finding the cancer earlier makes it much more likely that the cancer can be cured.
Breast cancer in Singapore has some features that distinguish it from patterns seen in Western populations, and these are clinically important for Singaporean women to understand.
- Age at diagnosis is younger in Singapore and across Asia. The median age at diagnosis for Singaporean women is approximately 53 -- roughly a decade younger than in Western populations. This makes screening from age 40 (rather than waiting until 50 as some international guidelines suggest) particularly important for Singaporean women.
- Dense breast tissue is more prevalent in Asian women. Dense breast tissue is a strong risk factor for breast cancer and also reduces mammogram sensitivity -- up to 20% of breast cancers in women with dense breasts may not be visible on mammography alone. Women with dense breasts may benefit from supplemental ultrasound screening.
- Despite breast cancer being the most common cancer in Singaporean women, mammography uptake remains below optimal levels, particularly in younger eligible women. Late-stage diagnosis is directly linked to delayed or absent screening.
Types of Breast Cancer
By tissue of origin
- Invasive ductal carcinoma (IDC): The most common type, accounting for approximately 80% of invasive breast cancers. Begins in the cells lining the milk ducts and invades through the duct wall into surrounding breast tissue.
- Invasive lobular carcinoma (ILC): The second most common type (~10-15%). Begins in the lobules (milk-producing glands). ILC often presents as a diffuse thickening rather than a discrete lump and can be more difficult to detect on mammography.
- Ductal carcinoma in situ (DCIS): Non-invasive. Abnormal cells confined within the milk duct that have not broken through into surrounding tissue. Often detected on mammography as microcalcifications. Highly curable with surgery and, where indicated, radiotherapy.
By biological subtype
The biological subtype -- determined by hormone receptor and HER2 status on biopsy -- is the most clinically important classification because it determines which targeted treatments are effective. This is the classification that guides the entire systemic treatment plan.
- Hormone Receptor-Positive (HR+): Approximately 70-80% of all breast cancers are hormone receptor-positive, meaning the tumour cells carry oestrogen receptors (ER+), progesterone receptors (PR+), or both. HR+ cancers are generally slower-growing and associated with a good prognosis.
- Hormone Receptor-Positive (HR+): HER2-positive breast cancer overexpresses the HER2 (Human Epidermal growth factor Receptor 2) protein, which drives aggressive cell proliferation.
- Hormone Receptor-Positive (HR+): Triple-negative breast cancer lacks oestrogen receptors, progesterone receptors, and HER2 overexpression. It cannot be targeted by hormone therapy or anti-HER2 agents. TNBC tends to be faster-growing, more likely to spread, and has historically been associated with a less favourable prognosis.
Staging of Breast Cancer
Stage 0 refers to non-invasive breast cancer such as ductal carcinoma in situ (DCIS) that is confined to the ducts. This means that cancerous or non-cancerous cells are localized and did not break out into neighboring breast tissues.
Stage I
Stage I breast cancer is invasive, which means that cancer cells have developed and spread to surrounding breast tissues.
Stage II
Stage II breast cancer is divided into subcategories - IIA and IIB.
IIA refers to invasive breast cancer where no tumor is located but cancer cells (larger than 2 mm) is found in 1 to 3 axillary lymph nodes under the arm or near the breast bone.
IIB refers to invasive breast cancer where the tumor is between 2-5 cm with small groups of cancer cells found in the lymph nodes. In some cases, the tumor can be larger than 5 cm but may not have spread to the axillary lymph nodes.
Stage III
Stage III breast cancer is divided into subcategories - IIA, IIB and IIC.
Stage IV
Stage IV breast cancer, also known as metastatic breast cancer, refers to invasive breast cancer that has spread beyond the breast and lymph nodes to other parts of the body such as the lungs, bones or brain.
Symptoms of Breast Cancer
Many breast cancers -- particularly early-stage cancers -- cause no symptoms at all and are discovered only on routine mammography. This is one of the strongest arguments for regular screening. When symptoms do occur, they may include:
- Changes in size, shape or appearance of breast
- Changes in surface of skin on the breast, such as skin that looks dimpled or looks like an orange peel
- Lump or thickened area of the breast that feels different from surrounding areas
- Nipple invertion
- Peeling, crusting, flaking skin around the areola or breast skin
- Axillary swelling -- swollen lymph nodes in the armpit may indicate breast cancer spread to the nodes
Risk factors of Breast Cancer?
Understanding your risk factors helps guide screening decisions but does not predict individual outcomes -- most women who develop breast cancer have no identifiable risk factors beyond being female and getting older.
Non-modifiable risk factors
- Female sex: Breast cancer is more common in women than men, though male breast cancer occurs and must not be dismissed
- Age: Risk increases progressively with age. The majority of breast cancers occur in women over 40.
- Dense breast tissue: Independently increases breast cancer risk and reduces mammogram sensitivity
- Family history: A first-degree relative with breast cancer doubles risk. Multiple affected relatives, younger age at diagnosis in family members, and male breast cancer in the family increase risk further.
- Dense breast tissue: Breast tissues are made of fatty tissues and dense tissues, with dense tissues being comprised of milk glands, milkd ducts, and fibrous tissues. Dense breast tissues can make it harder to detect breast cancer on a mammogram.
- Genetic mutations: BRCA1 confers 50-70% lifetime risk; BRCA2 40-60%. Other genes including PALB2, CHEK2, ATM, and CDH1 carry intermediate risk.
- Personal history: Prior breast cancer, DCIS, or certain benign breast changes (atypical hyperplasia, lobular carcinoma in situ) increase future risk
- Reproductive history: Early menarche (before age 12), late menopause (after 55), nulliparity, or first pregnancy after 30 increase cumulative oestrogen exposure
Modifiable risk factors
- Alcohol consumption: Each standard drink per day increases breast cancer risk by approximately 7-10%. Alcohol is a clear, dose-dependent risk factor.
- Obesity: Particularly post-menopausal obesity, as adipose tissue converts androgens to oestrogen
- Physical inactivity: Regular exercise reduces breast cancer risk by 10-20%
- Hormone therapy: Combined oestrogen-progesterone hormone replacement therapy (HRT) increases risk with extended use. The risk returns to baseline after stopping.
- Smoking: Associated with a modest increase in breast cancer risk, particularly with smoking beginning before first pregnancy
Screening: Detecting Breast Cancer Before Symptoms
Screening mammography remains the gold standard for breast cancer early detection and is the primary reason breast cancer survival rates have improved dramatically over the past 30 years.
Mammography
Annual mammography screening is recommended for women aged 40 and above. Farrer Park Hospital uses advanced mammography technology that covers a large area of the breast in a single image and uses 40% less radiation compared to standard systems. The procedure involves brief, firm compression of each breast -- this is necessary to obtain a clear image and is momentarily uncomfortable but not harmful.
Digital breast tomosynthesis (3D mammography) is increasingly available and offers improved detection, particularly in women with moderately dense breasts, by producing multiple thin slice images rather than a single flat image.
Breast ultrasound
Breast ultrasound is used as a supplement to mammography, not a replacement. It is particularly valuable for women with dense breast tissue (in whom mammography sensitivity is reduced), for assessing a specific area of concern identified clinically or on mammography, and for guided biopsy procedures. In Singapore, where dense breast tissue is common, supplemental ultrasound screening is increasingly part of the routine breast health assessment.
Breast MRI
Breast MRI is the most sensitive breast imaging modality and is recommended for annual screening in women at high risk -- BRCA mutation carriers, women who received chest radiation before age 30, and those with a strong family history and lifetime risk above 20-25%. MRI is not recommended as routine screening for average-risk women due to a higher rate of false-positive findings.
Breast self-examination (BSE)
Women aged 20 and above are encouraged to perform monthly breast self-examination -- ideally one week after the period ends, when the breast is least tender. BSE does not replace mammography but helps women become familiar with their own breast tissue so they can recognise changes and seek assessment promptly. Any new, persistent change found on self-examination should be assessed by a doctor.
Breast Cancer Diagnoses
- Clinical Breast Examination: A thorough physical examination of both breasts, axillae, and supraclavicular areas. Assesses lump characteristics (size, consistency, mobility, skin changes) and lymph node status. Always performed alongside imaging.
- Mammography: Standard bilateral two-view mammography. The primary screening and diagnostic imaging tool. Identifies masses, microcalcifications, and architectural distortions. Sensitivity is reduced in dense breast tissue.
- Breast Ultrasound: Characterises lesions identified on mammography or clinical examination. Distinguishes solid masses from cysts. Essential for dense breasts and for ultrasound-guided biopsy.
- Breast MRI: Used for high-risk screening, pre-operative extent of disease assessment, and when mammography and ultrasound are inconclusive. Most sensitive but less specific -- higher false-positive rate.
- Core Needle Biopsy: The standard diagnostic biopsy. A hollow needle removes small cores of tissue from the lesion under ultrasound or mammographic guidance. Provides tissue for full histological analysis including ER, PR, HER2 testing, and tumour grade.
- Fine Needle Aspiration: A smaller needle aspirates cells from a lesion. Faster than core biopsy but provides cytology (cells) rather than histology (tissue architecture). Used for lymph node assessment and cyst aspiration.
- Staging CT Scan: CT of chest, abdomen, and pelvis for staging purposes in confirmed breast cancer. Assesses for lymph node involvement, lung, liver, and bone metastases. Performed when lymph node involvement or high-risk features are identified.
- Bone Scan/PET-CT: Bone scan or PET-CT to detect bone metastases. PET-CT is increasingly used for staging of locally advanced breast cancer given its superior sensitivity for lymph node and distant metastatic disease.
