A breast lesion is a general term used by healthcare providers to describe any abnormal area, lump, or change found within the breast tissue. It functions as a descriptive label for a finding on an exam or imaging test, rather than a specific medical diagnosis itself. Because the term is broad, it encompasses a wide range of conditions. Most lesions are non-cancerous, but some may be malignant.
How Breast Lesions Are Identified
Lesions are often discovered through self-examination, clinical breast examination (CBE), or screening imaging. Individuals may notice a lump, change in contour, or area of thickening during a self-examination. A CBE performed by a healthcare professional can also detect a lesion through physical palpation.
Many lesions are first identified through screening mammography, which detects abnormalities too small to be felt. If an abnormality is seen, additional diagnostic imaging is ordered to obtain a clearer picture. This often includes an ultrasound, which uses sound waves to determine if the lesion is solid or a fluid-filled sac. Advanced imaging like Magnetic Resonance Imaging (MRI) may also be used to better define the suspicious area.
Understanding the Types of Breast Lesions
Once identified, a lesion is categorized based on its cellular composition to determine if it is benign (non-cancerous) or malignant (cancerous). The majority of breast lesions are benign. These non-cancerous findings often arise from normal physiological changes, such as hormonal fluctuations.
Benign (Non-Cancerous) Lesions
One frequent benign finding is a breast cyst, a fluid-filled sac resulting from fluid accumulation in the milk ducts. Cysts are common in women aged 35 to 50 and may become tender or change size in response to the menstrual cycle. Another common type is a fibroadenoma, a solid, non-cancerous tumor composed of fibrous and glandular tissue. Fibroadenomas typically feel smooth, firm, rubbery, and are often freely movable.
Other non-cancerous lesions include simple hyperplasia, a mild overgrowth of cells in the breast ducts or lobules, and fat necrosis, scar tissue formation occurring after trauma or injury. While not malignant, certain forms of atypical hyperplasia involve distorted or abnormal cells. These findings may slightly increase the future risk of developing breast cancer and often require closer monitoring or removal.
Malignant (Cancerous) Lesions
Malignant lesions represent uncontrolled cell growth and are classified by where the abnormal cells originate. The most common form is invasive ductal carcinoma (IDC), which begins in the milk ducts and spreads into the surrounding fatty tissue. IDC makes up the majority of all breast cancer cases. Another type is invasive lobular carcinoma (ILC), which starts in the milk-producing glands (lobules) before spreading.
Before becoming invasive, a lesion may be classified as ductal carcinoma in situ (DCIS). DCIS is a non-invasive, pre-invasive (Stage 0) condition where cancerous cells are contained entirely within the milk ducts. The presence of any malignant or high-risk lesion requires a formal tissue diagnosis to guide the treatment plan.
Definitive Diagnosis Procedures
The only way to definitively determine if a suspicious lesion is benign or malignant is through a biopsy procedure. A biopsy involves removing a small sample of the abnormal tissue for examination by a pathologist. The choice of procedure depends on the lesion’s characteristics, including its size, location, and whether it is solid or cystic.
A common method is a core needle biopsy (CNB), which uses a hollow needle to extract several small cylinders of tissue. CNB is highly accurate and provides sufficient tissue to differentiate between invasive and non-invasive disease, and to perform hormone receptor status tests. For small or non-palpable lesions, the procedure is performed under continuous imaging guidance, such as ultrasound or stereotactic mammography, to ensure precise needle placement.
A fine-needle aspiration biopsy (FNAB) may be used, employing a thin needle to draw out individual cells or fluid. Another technique is a vacuum-assisted biopsy (VAB), which uses a vacuum device to collect multiple tissue samples through a single, small incision. Once collected, the pathologist analyzes the cells under a microscope, looking for abnormal cell architecture and growth patterns to provide the final diagnosis.