A mole is a common skin growth, appearing as a cluster of pigmented cells that can range in color from tan to brown or black. While many moles are harmless, observing a new or changing mole, particularly on a visible area like the thumb, can cause concern. Moles in specific body locations do warrant a closer look from a healthcare professional.
The Significance of Moles on Hands and Feet
Moles appearing on the palms of the hands, soles of the feet, or underneath the fingernails or toenails are referred to as “acral” moles. This specific location holds particular importance because a less common but more aggressive form of skin cancer, known as acral lentiginous melanoma (ALM), is more likely to develop in these areas. Unlike other types of melanoma, ALM is not primarily linked to sun exposure, meaning it can affect individuals regardless of their sun exposure habits. This type of melanoma can also affect people of all skin tones, including those with darker complexions, where it may be the most common form of melanoma diagnosed.
Identifying Concerning Features
Recognizing changes in moles is an important step in skin health. The “ABCDE” rule provides a helpful guide for identifying potentially concerning features:
Asymmetry: One half of the mole does not match the other half.
Border: May appear irregular, notched, or blurred, rather than smooth and well-defined.
Color: Displays multiple shades of brown, black, or even areas of white, red, or blue within the same lesion.
Diameter: Larger than 6 millimeters, roughly the size of a pencil eraser, is also a warning sign, although melanomas can sometimes be smaller.
Evolving: Refers to any change over time in the mole’s size, shape, color, elevation, or new symptoms like itching or bleeding.
Beyond the general ABCDE guidelines, specific signs are particularly relevant for moles located on the thumb or other acral areas. A new streak of pigment that appears underneath the fingernail or toenail, especially if it grows wider or causes the nail to crack or break, is a significant indicator. This specific nail discoloration, which may extend from under the nail to the surrounding skin of the nail fold, is known as Hutchinson’s sign and is considered a clue for subungual melanoma. Any new, unexplained pigmentation on the thumb’s skin or nail bed, or an existing spot that feels different or looks unlike other moles on the body, should prompt further evaluation.
When to Consult a Dermatologist
Self-assessment tools, while helpful, cannot replace a professional medical evaluation. Any mole on the thumb that exhibits concerning features, particularly if it is new or changing, should be examined by a dermatologist. During an appointment, the dermatologist will perform a thorough visual examination of your skin, which may involve using a special magnifying tool called a dermatoscope to inspect the mole in greater detail. This device allows the doctor to see patterns within the mole that are not visible to the naked eye. If a mole appears suspicious, the dermatologist may recommend a biopsy, which involves removing a small tissue sample for laboratory analysis to determine if cancer cells are present. Early detection of melanoma, including acral lentiginous melanoma, is associated with more effective treatment outcomes.