Seborrheic Keratosis is Benign
Seborrheic keratosis (SK) is a benign epidermal tumor with no malignant potential. 1, 2
Nature of the Lesion
- SK is the most common benign epidermal keratinocytic tumor in clinical dermatological practice, occurring predominantly in adults over age 50 1, 3
- The lesion is purely benign with no risk of malignant transformation, despite the presence of oncogenic mutations (such as FGFR-3) that have been detected in SK lesions 2, 4
- SK can occur on all body areas except palms and soles, with the face and upper trunk being the most common sites 1
Critical Diagnostic Pitfall: Mimicry of Malignancy
While SK itself is benign, the major clinical concern is that SK can mimic melanoma or squamous cell carcinoma, and conversely, skin cancers can mimic SK or arise in association with SK 3. This creates a significant diagnostic challenge:
- Irritated seborrheic keratosis can show inflammation with itching, leading to confusion with melanoma 5
- Cases of melanoma mimicking seborrheic keratosis have been documented, highlighting the risk of misdiagnosis based solely on visual assessment 6
- The presence of pruritus (itching) in SK lesions is common and was historically overemphasized as a melanoma warning sign, leading to excessive referrals 5
When to Biopsy Despite Benign Nature
For uncertain diagnosis, complete excision with a narrow rim (2 mm) of normal skin should be performed, with tissue sent for histopathological examination 6. This is critical when:
- The lesion demonstrates atypical features that could represent melanoma (asymmetry, irregular borders, heterogeneous color, large diameter, recent evolution) 7
- Deep learning algorithms and dermatoscopy can improve diagnostic accuracy in differentiating SK from malignant keratinocyte lesions and melanoma 7
- Dermoscopy is the preferred non-invasive diagnostic method, particularly to differentiate pigmented SKs from melanoma 2