Yes, seborrheic keratoses do grow. They are slow-growing lesions that gradually increase in both size and thickness over several years. Most stay under 4 cm in diameter, and they rarely shrink or disappear on their own. The growth is typically so gradual that you may not notice changes from week to week, but comparing a lesion to how it looked a year or two ago often reveals a difference.
How Seborrheic Keratoses Grow
These lesions expand in two directions. They spread outward across the skin’s surface, and they also build upward, becoming thicker and more raised over time. A spot that starts as a flat, lightly pigmented patch can eventually develop into a bumpy, waxy-textured growth with a characteristic “stuck-on” appearance. The surface may become rougher or develop small crevices as the lesion matures.
Along with size changes, the color can shift. Seborrheic keratoses range from light tan to dark brown or black, and older lesions tend to be darker and more textured than newer ones. This color change is part of normal progression, not necessarily a sign of anything dangerous, though darkening is one reason these growths sometimes get mistaken for melanoma.
How Large They Can Get
The vast majority of seborrheic keratoses stay relatively small. Anything under 4 cm is considered typical. But in rare cases, they can grow much larger. Case reports of “giant” seborrheic keratoses document lesions ranging from 4.5 cm to 25 cm at their widest, with an average size of about 9.8 cm. One documented case measured 7.5 × 7 × 1.5 cm and had a cauliflower-like surface with visible fissures. These extreme cases are uncommon and usually prompt a biopsy to rule out other conditions.
Growth Over a Lifetime
Seborrheic keratoses are the most common benign skin growths, and they become nearly universal in people over 40. Both the number and size of lesions increase with age. Someone in their 40s might have a handful of small spots, while someone in their 70s could have dozens, with the older lesions noticeably larger and thicker than newer ones. New lesions also continue to appear throughout life, so the total count climbs steadily with each decade.
When Growth Is a Warning Sign
Slow, steady growth over years is expected and not a cause for concern. What does warrant attention is a sudden change in pattern: rapid growth of an existing lesion, or the abrupt appearance of many new seborrheic keratoses within a short period.
The sudden eruption of multiple seborrheic keratoses, particularly within a span of months rather than years, is known as the Leser-Trélat sign. This is a rare phenomenon linked to internal cancers. Unlike typical seborrheic keratoses that develop gradually over several years, Leser-Trélat lesions go from first appearance to widespread involvement frequently within a single year. The association remains somewhat debated among dermatologists because it’s difficult to study rigorously, but the pattern is considered worth investigating when it occurs.
Other changes that deserve a closer look include bleeding, crusting, or sores on the surface of an existing lesion, a noticeable shift in color or shape, and persistent itching or redness around the growth. These features can sometimes signal that what looks like a seborrheic keratosis is actually something else, including melanoma. Some melanomas mimic the appearance of seborrheic keratoses closely enough that even experienced clinicians rely on magnified skin exams to tell them apart.
Distinguishing Growth From Something Serious
The features that help separate a growing but harmless seborrheic keratosis from a melanoma are mostly about pattern. Seborrheic keratoses tend to have a uniform, waxy texture with a well-defined border and a consistent surface. Melanomas, even when they resemble keratoses, more often show irregular pigment patterns, uneven coloring with blue-white areas, and abnormal blood vessel patterns visible under magnification.
A study examining melanomas that were clinically mistaken for seborrheic keratoses found that 86.7% had irregular pigmentation, 50% had atypical pigment networks, and 33% showed regression structures when examined closely. Every single case in that series had at least one feature that flagged it for removal. The takeaway: a growth that looks “off” compared to your other seborrheic keratoses, even subtly, is worth having examined.
What Happens After Removal
If a seborrheic keratosis is removed for cosmetic reasons or because it’s irritated, it can sometimes come back in the same spot. The recurrence rate depends on the method used. Cryotherapy (freezing) has a higher recurrence rate than physical removal with a sharp instrument. One comparison found laser treatment achieved a 100% clearance rate with less post-treatment darkening of the skin, while cryotherapy succeeded only 68% of the time. Removal does not prevent new seborrheic keratoses from forming elsewhere, since the underlying tendency to develop them continues with age.