Breast asymmetry refers to a difference in size, shape, or position between an individual’s two breasts. It is very common among women.
Understanding Breast Asymmetry
Some degree of breast asymmetry is a normal variation, affecting many women. This can often be observed during puberty, as breasts may develop at different rates, or it can occur due to hormonal fluctuations throughout life, such as during the menstrual cycle, pregnancy, or menopause. Approximately 90% of women have at least a 10-20% difference in breast volume. This natural unevenness is often subtle and not a cause for concern.
However, certain characteristics of breast asymmetry may warrant medical attention. These include new onset asymmetry, a noticeable increase in asymmetry over time, or asymmetry accompanied by other physical changes. Such changes might involve a palpable lump, alterations in skin appearance like dimpling or redness, nipple changes such as inversion or discharge, or persistent breast pain. A significant or suddenly appearing asymmetry could indicate an underlying issue requiring evaluation.
Causes of Significant Asymmetry
When breast asymmetry is new or progressive, it can be linked to various underlying medical conditions, both benign and, less commonly, malignant. Benign causes are non-cancerous and include common breast changes. These may involve cysts (fluid-filled sacs) or fibroadenomas (non-cancerous solid lumps). Hormonal changes, infections, or even trauma to the breast can also lead to changes in size, shape, or density.
Breast asymmetry can sometimes manifest as specific developmental conditions, such as juvenile hypertrophy, where one breast grows significantly larger during puberty. Other benign conditions like dense stromal fibrosis (where connective tissue is denser in one area) or pseudoangiomatous stromal hyperplasia (a non-cancerous growth of cells) can also contribute to asymmetry. While many causes are benign, breast cancer can also present as new or progressive asymmetry, making medical evaluation important.
Medical Evaluation of Breast Asymmetry
When a healthcare provider evaluates breast asymmetry, the process typically begins with a physical examination of the breasts to assess any visible changes or palpable lumps. This initial assessment helps determine the nature and extent of the asymmetry. Following the physical exam, imaging tests are commonly utilized to gain a more detailed view of the breast tissue.
A mammogram is often the first imaging test, which can reveal differences in breast density or the presence of a mass. If a mammogram identifies an area of asymmetry, especially a “developing asymmetry” (new or larger compared to previous images), further evaluation is recommended. This may include additional mammographic views to clarify the finding.
An ultrasound may be performed to further investigate areas of concern identified on a mammogram or during a physical exam. This imaging technique can help distinguish between solid masses and fluid-filled cysts. For some cases, particularly in individuals with dense breast tissue or those at high risk for breast cancer, a breast MRI might be used to detect abnormalities not visible with other methods. If suspicious findings persist after imaging, a biopsy (taking a small tissue sample for laboratory analysis) is the definitive way to determine if cancer cells are present.