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8/8/2019 Seborrheic Keratosis: A Pictorial Review of the Histologic Variations
http://slidepdf.com/reader/full/seborrheic-keratosis-a-pictorial-review-of-the-histologic-variations 1/6
The Internet Journal of Dermatology 2009 : Volume 7 Number 2
Sebor rh eic Ker atosis: A Pictor ial Review of theHistopathologic Variations
Deba P Sar ma MD
Department of Pathology
Creighton University Medical Center
Omaha NE USA
Susan Repertinger MD
Department of Pathology
Creighton University Medical Center
Omaha NE USA
C i t a t i o n : D. Sarma & S. Repertinger : Seborrheic Keratosis: A Pictorial Review of the Histopathologic Variations. The Internet Journal
of Dermatology . 200 9 Volume 7 Number 2
Keywords: seborrheic keratosis | seborrheic keratosis variations | seborrheic keratosis microscopic images
Abstract
A brief review of the variations of microscopic appearances of seborrheic keratosis is presented.
Seborrheic keratosis: Acanthotic type (Figure 1)
Although no exact data are available for percentage distribution of different histologic subtypes of seborrheic
keratosis, the acanthotic type appears to be the most common. This type shows marked acanthosis of predominantly
basaloid cells [1]. Moderate papillomatosis and hyperkeratosis are present and characteristic horn cysts or
8/8/2019 Seborrheic Keratosis: A Pictorial Review of the Histologic Variations
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pseudocysts are seen. Aproximately one-third of these lesions exhibit melanocyte proliferation and
hyperpigmentation., demonstrating the common finding of overlapping histologic findings between different subtypes.
Squamous eddies are absent.
Seborrheic keratosis: Hyperkeratotic type (Figure 2)
Pronounced papillomatosis is present in the hyperkeratotic form of seborrheic keratosis [1]. Acanothosis is mild, but
shows a verrucous appearance with elongated projections (“church spire” pattern). There is pronounced
orthohyperkeratosis. While horn cysts and pseudocyts may be seen, they are less common than in the acanthotic
form. Hyperpigmentation is unusual.
Seborrheic keratosis: Clonal type (Figures 3 and 4)
The hallmark of the clonal (nested) seborrheic keratosis subtype is the proliferation of sharply demarcated
intraepithelial nests of basaloid or pale cells (Borst-Jadassohn phenomenon). In some cases the nests are composed of
larger cells with conspicuous intercellular bridges, with nests separated by strand of cells with small dark nuclei.
8/8/2019 Seborrheic Keratosis: A Pictorial Review of the Histologic Variations
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Seborrheic keratosis: Flat clonal type (Figures 5 and 6)
Flat seborrheic keratosis of clonal type shows acanthosis and intraepithelial nests of basaloid or pale cells. However,
papillomatosis and hyperkeratosis is not prominenent. This variant may be confused histologically with melanocytic
nevus or malignant melanoma by the inexperienced.
Seborrheic keratosis: Reticulated type (Figures 7 and 8)
The reticulated (or adenoid) type is characterized by numerous, thin, double rows of basaloid epidermal cells which
extend from the epidermis and show branching and interweaving in the dermis. Hyperpigmentation is relatively
common, although horn cysts and pseudocysts are not [1]. There is clinical and histologic evidence of a relationship
8/8/2019 Seborrheic Keratosis: A Pictorial Review of the Histologic Variations
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between solar lentigo and the reticulated subtype of seborrheic keratosis; solar lentigo may even become a reticulated
seborrheic keratosis through exaggerated downward budding of basal cells.
Seborrheic keratosis: Irritated type (Figures 9 and 10)
Irritated seborrheic keratosis shows a lichenoid inflammatory infiltrate in the dermis and intraepithelial squamous
eddies [1], which are composed of whorling aggregates of eosinophilic squamous cells. In this type, the squamous cells
outnumber the basaloid cells. Most eddies appear to show at least one of the morphological features of intraepidermal
hairr follicle structures [2]. Squamous eddies may be confused with horn pearls of squamous cell carcinoma, but can be
differentiated from them by their large number, small size, and circumscription. Other features of irritated seborrheic
keratosis include apoptotic cells in the basal layer and occasional acantholysis, dyskeratosis, and spongiosis.
Seborrheic keratosis: Pigmented type (Figures 11 and 12)
8/8/2019 Seborrheic Keratosis: A Pictorial Review of the Histologic Variations
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Pigmentation is often seen within the acanthotic and reticulated subtypes of seborrheic keratosis. Pigment is present
mainly within basal keratinocytes, although in melanoacanthoma, a rare type of pigmented seborrheic keratosis, a
marked increase in melanocytes containing melanin pigment is seen. The pigmented subtype may be clinically
confused with other pigmented lesions, such as malignant melanoma, pigmented basal cell carcinoma, or melanocytic
nevus.
Seborrheic keratosis: Acantholytic type (Figures 13 and 14)
The acantholytic subtype usually incorporates features of other subtypes, particularly of the irritated type, and are
located on the face and scalp (65%) [3]. Acantholysis is seen almost exclusively in the squamous nests showing
dyskeratosis and spongiosis between and around squamous eddies or horn cysts. It is speculated that the
dyskeratotic, degenerative changes of keratinocytes, together with the spongiosis, are responsible for the acantholysis.
Correspondence to
Deba P Sarma, M.D.
Department of Pathology
Creighton University Medical Center
Omaha, NE, USA
References
1. Hafner, C. and T. Vogt. Seborrheic keratosis. J Dtsch Dermatol Ges, 2008. 6(8): 664-77. (s)
8/8/2019 Seborrheic Keratosis: A Pictorial Review of the Histologic Variations
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2. Choi HJ, Yun SK, Kim HU, Ihm CW. Squamous eddies in irritated seborrheic keratosis. Am J Dermatopathol 2007.
29(1): 28-31. (s)
3. Chen M, Shinmori H, Takemiya M, Miki Y. Acantholytic variant of seborrheic keratosis. J Cutan Pathol 1990. 17(1):
27-31. (s)
4. Lever’s Histopathology of the Skin, Elder DE, Editor, 10th Edition, 2008 by Lippincott Williams and Wilkins. (s)
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