Solar lentigines, seborrheic keratoses, and lichenoid keratoses represent a spectrum of benign epidermal and keratinocytic lesions with overlapping dermoscopic features. Recognition of pattern-based clues—rather than single findings—is key to accurate diagnosis, especially in sun-damaged skin.
Fine, parallel, lightly pigmented brown lines
May be straight or slightly curved
Resemble dermatoglyphic “fingerprint” ridges
Common in early or classic solar lentigo
Irregular, scalloped, or notched lesion edges
Background of homogeneous light brown pigmentation
Classic for benign lentiginous proliferation
Abrupt cut-off at lesion border
Round or smoothly curved outline
Pigmentation extends cleanly to edge
Homogeneous brown pigmentation without internal structures
Absence of pigment network or globules
Typically lacks melanoma-specific features
Smudged or blurred appearance of pigment
Gives impression of soft, diffused pigmentation rather than structured pattern
Prominent pigmented network with thick and thin lines
Jagged, irregular terminal ends
Abrupt cut-off at periphery
Dark, “ink spill” appearance
White to yellow, round, bright structures
Well-circumscribed keratin-filled cysts
Best visualized in non-polarized dermoscopy
Round to oval invaginations
Brown, black, or yellow keratin-filled pits
Represent epidermal keratin accumulation
Linear or curvilinear grooves
Brown, black, or yellow keratin-filled clefts
Epidermal invaginations
Often enhanced with UV light
Raised, rounded projections
Broad, short “sausage-like” structures
Contribute to cerebriform architecture
Combination of fissures and ridges
Resembles brain-like surface architecture
Highly suggestive of seborrheic keratosis
Parallel looped (U-shaped) vessels
Surrounded by a white keratin halo
May be diffuse rather than peripheral
Not specific but supportive in keratinized lesions
Ink tends to collect in fissures and comedo-like openings
Can help highlight SK architecture
May otherwise mimic pigment network or globules
Lichenoid keratosis represents regression of a pre-existing lesion such as a solar lentigo or seborrheic keratosis, and can mimic melanoma or other malignancies in sun-damaged skin.
Gray or brown lesion
Pinkish thin plaque
Often solitary and evolving
Actinic keratosis
Basal cell carcinoma
Squamous cell carcinoma
Melanoma
Seborrheic keratosis / lentigo
Atypical melanocytic proliferation
Coarse gray granules > fine granules
Evenly distributed gray pigmentation
Reflects melanophages in dermis
Gray dots and granules with focal clumps of pigment
Histologic correlate: dermal melanophages
Regression in melanoma tends to show a fine granular pattern
Lichenoid keratosis more commonly demonstrates a coarse diffuse granular pattern