Correlation of seborrheic keratosis
Fissures and ridges
Fissures and ridges describe multiple thick lines that resemble the gyri (ridges) and sulci (fissures) of the brain (Kittler et al., 2016; Malvehy et al., 2006). Histopathologically, they correspond to epidermal clefts filled with keratin (Minagawa, 2017).
Milia-like cysts
Milia-like cysts are whitish or yellowish round structures. Under non-polarized dermoscopy these structures shine brightly (Braun et al., 2011). Histopathologically, they reveal intraepidermal keratin pseudocysts (Minagawa, 2017). Milia-like cysts are highly suggestive of SK, but can be observed in BCC and papillomatous melanocytic lesions, including melanoma (Carrera et al., 2017).
Comedo-like openings and crypts
Comedo-like openings are dark (brown/black) round to oval invaginations. Crypts are similar, but more elongated and larger (Kittler et al., 2016a). Histologically, they reveal epidermal invaginations filled with keratin (Minagawa, 2017). They are associated with SKs, although can be seen in any papillomatous lesion, such as intradermal nevi and melanoma (Carrera et al., 2017).
