Investigations
Investigations to consider
dermoscopy
Test
The diagnosis of seborrhoeic keratosis is generally made clinically, but dermoscopy is increasingly used in primary and secondary care to differentiate between benign and malignant pigmented lesions. The UK National Institute of Health and Care Excellence guidance recommends that any patient undergoing a specialist assessment for pigmented lesions must be examined with a dermatoscope.[24]
The characteristic dermoscopic features of seborrhoeic keratosis are milia-like cysts and comedo-like openings. Milia-like cysts are white or yellowish round structures that correspond to small intra-epidermal, keratin-filled cysts (horn pearls). They are not exclusively found in seborrhoeic keratosis as they are also seen in congenital nevi and papillomatous dermal nevi, but less frequently. Comedo-like openings (also called pseudofollicular openings or crypts) are brownish holes in the surface of seborrhoeic keratosis that correspond histologically to keratin-filled invaginations of the epidermis.[26][29][30]
Result
features of seborrhoeic keratosis
biopsy and histopathological examination
Test
Biopsy is recommended in any isolated dark seborrhoeic keratosis, or where there is otherwise clinical suspicion for malignancy (e.g., lesions that itch or bleed, or become inflamed and red).[28] Sharply defined exophytic lesions growing intra-epidermal proliferations composed of mature basaloid cells. The characteristic histological features are keratin-filled invaginations and small cysts (horn cysts). Hyperkeratosis is present in variable degrees.
Result
features of seborrhoeic keratosis
reflectance confocal microscopy (RCM)
Test
RCM is a non-invasive imaging method that allows the in vivo examination of skin at cellular-level resolution. RCM features that indicate the diagnosis of seborrhoeic keratosis are: cerebriform surface structures; keratin-filled invaginations; corneal pseudocysts; a regular honeycomb pattern at epidermal layers; cords and polymorphous papillae at the dermo-epidermal junction; melanophages and looped vessels at the papillary dermis; and the absence of RCM features suggestive of malignancy.[27]
Result
features of seborrhoeic keratosis
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