A lump or mass in the breast is one of the most common symptoms that lead women to get examined for breast cancer. However, while finding a lump is an important warning sign, not all lumps mean cancer. In fact, most breast lumps are caused by benign (non-cancerous) changes or conditions.
The size of a lump is one factor that doctors consider when evaluating breast changes. But breast lumps and masses can vary greatly in size. Some are very small and can only be felt by doing a breast self exam. Others are quite large and visible on inspection or on a mammogram. So the question is – are cancerous lumps always big?
Breast Lump Basics
First, it helps to understand what breast lumps are and what causes them. A breast lump is simply an abnormal mass or swelling within the breast tissue. There are a variety of conditions that can cause benign breast lumps, including:
- Cysts: fluid-filled sacs that often feel smooth, firm and movable
- Fibroadenomas: solid, rubbery masses made up of normal breast tissue
- Fibrocystic changes: wider areas of lumpiness and thickening
Cancerous breast lumps may be caused by different types of breast cancer. The most common is invasive ductal carcinoma, which forms in the milk ducts. Less common types are invasive lobular carcinoma (forms in the milk glands) and inflammatory breast cancer.
Size of Benign vs. Cancerous Lumps
Both benign and cancerous lumps can range widely in size – from tiny, barely palpable masses to very large lesions. Here is an overview of the size range of common benign lumps and cancerous tumors:
Typical Size of Benign Lumps
- Cysts: Often less than 2 cm, but can grow larger
- Fibroadenomas: Usually 1-3 cm when first noticed
- Fibrocystic changes: Can involve single lumps or larger areas of thickening
Typical Size of Cancerous Lumps
- Ductal carcinoma in situ (DCIS): Often very small, less than 1 cm
- Early stage invasive ductal carcinoma: May be tiny, only a few mm, when first detected
- Later stage invasive cancers: Tend to be larger, 1 cm or greater
- Inflammatory breast cancer: Typically involves swelling and redness of much of the breast rather than a distinct lump
As this comparison shows, both cancerous and benign breast lumps can be small or large. There is a great deal of variability.
Small Cancerous Lumps
Small lumps are in fact very common with certain types of breast cancer:
DCIS
Ductal carcinoma in situ (DCIS) is a non-invasive form of breast cancer that arises in the milk ducts. By definition, it has not spread beyond the ducts into other breast tissue. DCIS lumps tend to be very small – often less than 1 cm. Microcalcifications (tiny specks of calcium) are sometimes the only sign of DCIS on mammography. However, these small DCIS lesions do need treatment because they can progress to invasive ductal carcinoma.
Early Stage Invasive Ductal Carcinoma
Even invasive ductal carcinoma is often small – less than 2 cm – when first detected. Some of these small invasive cancers are found incidentally on biopsy when a woman has a benign palpable lump or suspicious area on mammogram. As imaging and biopsy techniques improve, more of these very small invasive cancers are being diagnosed before they grow large or spread.
Triple Negative Breast Cancers
An aggressive form of invasive ductal carcinoma is triple negative breast cancer. This subtype is more common in younger women and African American women. One feature is that triple negative tumors often do not form a distinct mass, and may instead appear as only slight abnormal thickening of the breast tissue. So a very small area of suspicion may signal this more dangerous cancer type.
Large Benign Lumps
On the flip side, some benign breast conditions can produce quite large lumps:
Giant Fibroadenomas
While ordinary fibroadenomas are usually 1-3 cm, “giant” fibroadenomas can grow to 5 cm or larger. Despite their size, these remain benign fibrous growths with clear borders. However, they may raise concerns on physical exam or imaging and require biopsy.
Complex Cysts
A simple cyst contains only fluid and has a thin wall. But “complex” cysts have thick walls, solid material inside, and irregular shapes. These complex cysts can reach several centimeters in diameter but are still non-cancerous. However, they have a higher risk of being malignant so often need biopsy.
Gynecomastia
In males, increase in glandular breast tissue is called gynecomastia. It often causes uniform enlargement but can also form large, discrete lumps exceeding 5 cm. Although gynecomastia is benign, mammography and biopsy are sometimes needed to confirm.
What Else Determines Cancer Risk?
While the size of a breast lump is important, other factors also affect the likelihood that it is cancer:
| Factor | Higher Cancer Risk | Lower Cancer Risk |
|---|---|---|
| Age | Over 50 | Under 50 |
| Menstrual status | Post-menopausal | Pre-menopausal |
| Breast density | Dense tissue | Scattered fibroglandular tissue |
| Borders | Irregular, poorly defined | Smooth, well-circumscribed |
| Texture | Hard, firm | Soft, cystic, rubbery |
| Fixation | Fixed to skin or muscle | Mobile |
| Nipple changes | Inversion, discharge, retraction | No nipple changes |
| Skin changes | Dimpling, redness, warmth | None |
| Location | Behind areola, central breast | Outer breast areas |
Other Red Flags
Other warning signs, in addition to a new lump, that increase suspicion for cancer include:
- Thickening or swelling of part of the breast
- Irritation or dimpling of breast skin
- Redness, scaliness, or nipple changes
- Nipple discharge (especially if bloody)
- New pain in one spot that doesn’t go away
Any of these signs warrants prompt medical evaluation.
How Lumps Are Evaluated
Finding a new lump or breast change nearly always leads to further testing. Here is the typical workflow:
Step 1: Physical Exam
The first step is an experienced provider doing a clinical breast exam. They note the location and characteristics of the mass and whether the mass seems consistent with potential cancers. Enlarged lymph nodes under the arm may also be felt.
Step 2: Imaging
Extra imaging like mammograms, ultrasounds and MRIs help pinpoint the size and shape of the mass. They look for other abnormalities and guide the biopsy.
Step 3: Biopsy
A sample of cells is withdrawn from the lump through a needle biopsy or surgical biopsy. This pathology result can definitively diagnose if cancer is present and what type.
Takeaway on Lump Size and Cancer Risk
In summary, breast cancerous lumps are not always big in size. Some small lumps or areas of thickening turn out to be early stage or aggressive cancers. Benign lumps can also grow quite large.
While size is one factor, the whole clinical picture matters most. Any new lump or suspicious change should prompt prompt evaluation. Early diagnosis leads to better outcomes. With triple negative breast cancers in younger women, even very small lumps may be a warning sign.
Being aware of normal breast tissue and reporting changes to your doctor right away are key. This allows the most curable cancers to be caught early. Both self breast exams and regular screening mammograms detect the subtle signs of cancer when treatment is most effective.
Conclusion
In conclusion, cancerous breast lumps do not have to be large in size to pose a threat. Smaller tumors that remain confined to the ducts or that have not spread far into breast tissue are often the most curable. Thanks to improved imaging tests and awareness, more breast cancers are being found at these early stages.
While cancerous lumps tend to be firmer, have irregular borders and be fixed in place, benign lumps have more fluid, rounded, mobile characteristics. But size alone does not differentiate between benign and malignant. Any new lump or suspicious change warrants medical evaluation, regardless of size. Being aware of normal breast tissue and reporting changes quickly to your doctor allows the earliest detection.