Breast Cancer Staging and Classification: What Patients Should Know

• Tumour size (T)
• Lymph node involvement (N)
• Presence of metastasis (M)

Staging is usually determined at diagnosis but may be refined after imaging scans, biopsy results or surgery when more detailed information becomes available.

What Is Cancer Classification?

Breast cancer classification refers to how doctors identify the specific type of breast cancer based on the tumour’s biological characteristics. Rather than treating breast cancer as a single disease, classification determines whether the tumour is:

• Hormone receptor–positive (ER/PR-positive)
• HER2-positive
• Triple-negative

Each subtype behaves differently and responds to different treatments. This information is obtained through biopsy and laboratory testing. It plays a key role in guiding personalised treatment decisions and predicting response to therapy.

Differences Between Breast Cancer Staging and Classification

Breast cancer staging and classification are often discussed together, but they answer two different clinical questions. Both are important because they help doctors choose the most effective treatment plan and better understand how the cancer may behave.

• Staging (Stage 0–IV): Describes how far the cancer has spread in the body based on tumour size, lymph node involvement and metastasis.
• Classification (Tumour subtype): Describes the biological type of breast cancer based on hormone receptor status (ER/PR), HER2 status or triple-negative features.

In simple terms, staging explains the extent of spread, while classification explains the tumour type and likely response to treatment.

What Are the Different Breast Cancer Stages?

Breast cancer staging helps doctors assess disease severity and determine the most appropriate treatment plan. Breast cancer is grouped into Stage 0 to Stage IV, with lower stages indicating localised disease and higher stages indicating more extensive spread.

Stage 0: Non-invasive cancer confined to the milk ducts or lobules (ductal carcinoma in situ).

Stage I–II: Early-stage breast cancer, usually confined to the breast with limited lymph node involvement.

Stage III: Locally advanced breast cancer involving multiple lymph nodes or nearby tissues.

Stage IV: Metastatic breast cancer, meaning the cancer has spread to distant organs such as the lungs, liver, bones or brain.

At Maven Surgery, we understand that every breast cancer diagnosis comes with questions, uncertainty and important decisions. That’s why our team is committed to providing clear guidance, thorough assessment and personalised treatment planning based on each patient’s stage and cancer type. The team is led by Dr Chong Chee Keong, a Member of the Singapore Medical Association and a former Associate Program Director of SingHealth’s Residency Program. Book a consultation with us for personalised, transparent and carefully guided breast cancer assessment and management.

Meet Our Specialist

Dr Chong Chee Keong Breast, Colorectal and General Surgeon MBBS (Singapore), FRCS (Edinburgh), FRCS (Glasgow), FAMS (Singapore) Specialist Accreditation in Intensive Care Medicine Specialists Accreditation Board, Medical Director & Senior Consultant

Dr Chong Chee Keong is a breast, colorectal and general surgeon with over 20 years of clinical experience. Dual-fellowship trained and highly accredited, he founded Maven Surgery with a commitment to elevating the standard of care for breast and colorectal cancers, the two most common cancers affecting women and men.

Dr Chong works closely with multidisciplinary teams of surgical, medical and radiation oncologists and remains actively involved in international cancer conferences to stay at the forefront of advancing techniques. He has a strong focus on minimally invasive surgery, recognising the importance of preserving self-image while maintaining treatment safety and effectiveness.