It is completely normal to have moles, known medically as nevi, anywhere on the body, including the area beneath the breasts. Moles are common skin growths, and most adults have several of them. Their presence in the inframammary fold, the skin crease under the breast, is simply a matter of chance and normal skin distribution. While moles are nearly always benign, it is important to understand how the unique environment under the breast might affect them.
The Biology of Mole Formation
Moles develop from a localized cluster of pigment-producing cells called melanocytes. These cells are normally distributed throughout the skin’s basal layer, producing melanin, the pigment responsible for skin, hair, and eye color. When melanocytes grow in a concentrated group rather than spreading evenly, they form a nevus.
The number of moles a person develops is influenced by genetic factors, meaning a tendency to have many moles can be inherited. Environmental factors, particularly ultraviolet (UV) radiation exposure from the sun or tanning beds, also play a significant role. UV light can damage the DNA of melanocytes, triggering their proliferation and leading to the formation of acquired moles.
Moles are categorized as either congenital (present at birth) or acquired (appearing later in life). The combination of a person’s inherited predisposition and their history of sun exposure largely determines the total number and location of these pigmented lesions. Most moles are stable and harmless, remaining benign throughout life.
Moles in Skin Folds and High-Friction Areas
The area beneath the breast is an intertriginous zone, meaning skin rests against skin. This location creates an environment characterized by chronic heat, trapped moisture from sweat, and constant mechanical friction from skin rubbing against itself or clothing. These factors do not cause a benign mole to become malignant, but they can cause irritation that mimics concerning changes.
A raised mole in this high-friction area is particularly susceptible to rubbing, which can lead to it becoming inflamed, itchy, or even bleeding. This chronic microtrauma can cause the mole to look temporarily swollen, red, or scabbed. The localized warmth and moisture also make the entire skin fold prone to secondary conditions like intertrigo, an inflammatory rash that can exacerbate irritation around an existing mole.
If a mole under the breast is frequently irritated, it may be painful or sore, which is distinct from the biological changes associated with skin cancer. A dermatologist may recommend removal of a chronically irritated mole, not because it is suspicious, but simply to alleviate the discomfort and prevent recurrent bleeding or minor infection.
Identifying Concerning Changes
While irritation is often benign, it is important to monitor moles regardless of their location for signs of potential malignancy using the ABCDE method of self-assessment. Asymmetry means one half of the mole does not match the other half if an imaginary line is drawn through it. Border irregularity refers to edges that are uneven, notched, or scalloped rather than smooth and well-defined.
Color variation involves the presence of multiple colors within the same mole, such as shades of brown, tan, black, white, blue, or red. Diameter is usually assessed by noting if the mole is larger than six millimeters, roughly the size of a pencil eraser, though small melanomas can occur. The letter E, Evolving, refers to any change in a mole’s size, shape, color, or elevation over a period of weeks or months.
Other evolving symptoms, such as new onset of itching, tenderness, bleeding, or crusting, should also prompt attention. Because the under-breast area is often hidden, it is necessary to perform a thorough monthly self-examination to catch subtle changes. If a mole exhibits any of these ABCDE features or persistent, non-healing irritation, a professional evaluation is warranted.
Professional Evaluation and Next Steps
If a mole under the breast displays any of the ABCDE signs or is persistently irritated, seeking a professional medical evaluation is necessary. A dermatologist is trained to distinguish between common, benign irritation and the subtle indicators of skin cancer. During an examination, the physician will perform a full-body skin check, including difficult-to-see areas like the inframammary folds and scalp.
A specialized handheld magnifying device called a dermatoscope is often used to examine the mole’s structure and pigmentation patterns beneath the skin’s surface, providing a more accurate assessment than the naked eye. If the mole is suspicious, a skin biopsy is the only way to definitively determine if cancer cells are present. This in-office procedure involves removing a small sample of the mole for microscopic analysis.
Depending on the mole’s appearance and depth, the dermatologist may perform a shave biopsy, excisional biopsy, or punch biopsy under local anesthesia to obtain a sufficient tissue sample for accurate diagnosis. For moles that are constantly being rubbed and irritated but are not suspicious, surgical removal can be performed to prevent future discomfort and eliminate the need for ongoing monitoring.