Seborrheic keratoses

From dermoscopedia

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Description This chapter describes the dermoscopyDermoscopy is a non invasive diagnostic method. criteriaThis glossary term has not yet been described. of seborrheic keratosisThis glossary term has not yet been described..
Author(s) Ralph P. Braun · Stephanie Nouveau · Sabine Ludwig
Owner Ralph Braun→ send e-mail
Status released
Status update May 28, 2017
Status by Ralph P. Braun
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Seb k schematic.jpg



Seborrheic keratosesThis glossary term has not yet been described. are benignThis glossary term has not yet been described. epithelial lesions that can appear on any part of the body except for the mucous membranes, palmsThis glossary term has not yet been described., and solesThis glossary term has not yet been described.. The lesions are quite prevalent in people older than 30 years. The etiology of seborrheic keratosesThis glossary term has not yet been described. remains unclear. Ultraviolet light exposure may be responsible for the development of some seborrheic keratoses because they appear to evolve from solar lentiginesThis glossary term has not yet been described.; however, many develop in areas of the skin naturally protected from ultraviolet light exposure, such as the inframammary (intertriginous) areas. Clinically, early seborrheic keratoses are light- to dark brown oval macules with sharply demarcated borders (solar lentigoThis glossary term has not yet been described.). As the lesionsprogress, they transform into plaques with a waxy or stuck-on appearance[1]. The surfaces of these lesions have a warty and keratotic appearance. Often, the lesions have follicular plugs scattered over their surfaces. The size of the lesions varies from a few millimeters to a few centimeters. Histologically, there are several distinct forms of seborrheic keratoses. In general, the lesions are characterized by papillomatous epidermal hyperplasia of uniform and monotonous keratinocytes and the presence of pseudocysts. The diagnosisThis glossary term has not yet been described. of most seborrheic keratoses is straightforward. However, some seborrheic keratoses, especially the deeply pigmented variant, can simulate malignantThis glossary term has not yet been described. melanomas. Thin, early lesions have moth-eaten borders and fingerprint-like structures as described above for solar lentigines. Thicker pigmented seborrheic keratoses have the typical dermoscopy features as follows [2]:

Milia-like cystsThis glossary term has not yet been described.:

They are white-to-yellow, round structures that appear very bright when contrasted with their dark brown or black surroundings. The presence of multiple milia-like cystsThis glossary term has not yet been described. in pigmented seborrheic keratoses conjures up an image of “stars in the sky.” Milia-like cysts can also be seen in nonpigmented seborrheic keratosis. Milia-like cysts can also be seen in other lesions such as basal cell carcinomais the most common skin cancer, and one of the most common cancers in the United States.[1] While BCC has a very low metastatic risk, this tumor can cause significant disfigurement by invading surrounding tissues and in melanocyticThis glossary term has not yet been described. lesions including congenital neviThis glossary term has not yet been described. and melanomaThis glossary term has not yet been described.. However, if the lesion is non-melanocytic and is not a basal cell carcinoma then the presence of milia-like cyst is diagnostic of seborrheic keratoses specially if more then three are seen. It is interesting to note that the quality of milia-like cysts appear somewhat different in seborrheic keratosis and melanocytic lesions. In melanoma and congenital nevi the cysts appear “starry”, which is defined as small, bright and sharp. In seborrheic keratosis they appear “cloudy”, defi ned as larger and hazier in appearance. Histologically, the cysts correspond to intraepidermal, keratin-filled cysts. It is important to be aware that milia-like cysts are more conspicuous with non-polarized dermoscopy and are often diffi cult to visualize with polarized dermoscopy.

Comedo-like openings[[Comedo like openings]]:

They are round to ovoid craters that have black or brown comedo like plugs. Histologically, they correlate with keratin-fi lled invaginations of the skin surface

Fissures and ridgeslines, curved and thick to describe the structural components of the pattern SK:

Fissures (sulci) are comedo-like openings[[Comedo like openings]], which are not round but rather linear and appear as dark brown to black linear to curvilinear structures within the lesion. The presence of numerous fissures and ridgeslines, curved and thick to describe the structural components of the pattern SK can result in the formation of network-like structuresThis glossary term has not yet been described. or result in a cerebriform patternIs a dermoscopy pattern that resembles the aspect of a brain. Commonly seen in seborrheic keratosis.. Histologically, they represent deep invaginations of the epidermis, fi lled with keratin.

Network-like structuresThis glossary term has not yet been described.:

Interlacing fissures and ridges can create an appearance of network-like structures. The quality of the grid of network-like structures in a seborrheic keratosis differs from the network grid seen in melanocytic neviThis glossary term has not yet been described. by being significantly larger. However, at times the network-like structure in a seborrheic keratosis can look very similar to that of a nevusThis glossary term has not yet been described.. Examining the lesion clinically via side lighting can make the ridges more evident, thereby making it easier to differentiate networklike ridges in seborrheic keratosis from pigment network seen in melanocytic lesions.

Cerebriform patternIs a dermoscopy pattern that resembles the aspect of a brain. Commonly seen in seborrheic keratosis.:

Multiple fissures (sulci) and ridges (gyri) may produce a cerebriform pattern, where the structures resemble sulci and gyri of the brain (brain-like appearancelines, curved and thick to describe the pattern and fissures and ridges (former synonyms “gyry and sulci” and “fat fingers”) to describe the structural components of the pattern SK). These features are generally associated with an acanthotic seborrheic keratosis.

Fat-fingers:

They are linear and wide dermoscopic structures corresponding to ridges. They often appear as short sausage-shaped structures. Colors of these structures vary from tan/brown, blue and can be hypopigmented. The name has been given to these structures because their shapes can resemble a straight finger (linear), bent finger (curvilinear), or finger tip (oval–circular).

Sharply demarcated borders:

As known from clinical examination, seborrheic keratosis often have sharply demarcated borders.

Typical hairpin blood vesselsThis glossary term has not yet been described. :

Some seborrheic keratoses are associated with hairpin vesselsThis glossary term has not yet been described.. These hairpin vessels can appear as perfect “U”-shaped vessels of as “U”-shaped vessels that are twisted upon themselves. Typical hairpin blood vessels have a whitish halo around the blood vessel corresponding to the surrounding keratin. It is important to note that some melanomas can have hairpin vessels, but these vessels generally do not have the surrounding white halo but, rather have a pink halo. Similar hairpin vessels on a pin. background can be seen in irritated seborrheic keratosis.

Wobble testThis glossary term has not yet been described.:

This is a dynamic test that can only be performed with a contact dermoscopy deviceThis glossary term has not yet been described.. The test is performed as follows: once the contact plate of the dermoscope is fi rmly pressed down (pressure in vertical direction) against the lesion, it is then moved slightly back and forth in the horizontal plane (parallel to the skin surface). Seborrheic keratosisThis glossary term has not yet been described. will appear to stick to the glass plate and move en bloc with the movement of the dermoscopic faceThis glossary term has not yet been described. plate. In other words, they will slide back and forth. In contrast, nevi will not move en bloc but, rather roll back and forth. In other words, intradermal nevi will wobble. Knowledge of the above-described dermoscopic features and patterns seen in seborrheic keratosis will often prove valuable in differentiating seborrheic keratoses from other lesions, including melanoma. However, irritated or traumatized seborrheic keratoses can mimic melanoma or squamous cell carcinomaThis glossary term has not yet been described.. In these cases the history of trauma or the presence of typical criteria for seborrheic keratoses in another part of the lesion might be comforting. However, it is important to remember that skin cancer can develop within a seborrheic keratosis, and thus a biopsy is justified for atypical appearing seborrheic keratosis.
References:
  1. An Atlas of Dermoscopy, Second Edition. Marghoob A. et al. CRC Press; 2012.
  2. Braun et al.: Dermoscopy of pigmented seborrheic keratosis: a morphological study. Arch Dermatol 2002;138:1556-60. PMID: 12472342.