Seborrheic keratosis

Seborrheic keratosis
	Diagnosis in short
	; Seborrheic keratosis. H&E stain.
LM	horn cysts, pigmented basal layer, hyperkeratosis
Subtypes	acanthotic seborrheic keratosis, reticulated seborrheic keratosis, irritated seborrheic keratosis, digitated seborrheic keratosis, stucco keratosis
LM DDx	actinic keratosis, verruca vulgaris, basal cell carcinoma (fibroepitheliomatous pattern) - for reticulated SK, melanocytic nevus, condyloma acuminatum, inverted follicular keratosis
Gross	raised lesion
Site	skin
Associated Dx	internal malignancy - if very many
Prevalence	very common
Prognosis	benign

Seborrheic keratosis, abbreviated SK, is a very common diagnosis is dermatopathology.

General

Benign.
Most common tumour in older people.^[1]
"Large number" of SKs = paraneoplastic syndrome (Leser–Trélat sign).^[2]

Epidemiology:

Old people.
Usually in sun exposed area.^[3]

Gross

"Stuck-on" appearance - raised lesion.

Image(s):

SK - gross image (dermatlas.org).

Microscopic

Features:^[2]

Raised above skin surface.
Border sharply demarcated.
Hyperkeratosis - stratum corneum extra thick.
- May be minimal.
Horn cysts - intraepidermal collections of keratin - key feature.
- Actually invaginations - not true cysts; thus, they may more accurately be called pseudohorn cysts.^[4]
Clusters of cells with brown granular material in the superficial dermis/dermoepidermal junction - pigmented melanocytes.

DDx:^[5]

Actinic keratosis - especially, irritated SKs; have nuclear atypia and parakeratosis.
Verruca vulgaris - SK may have papillomatous projections.
Basal cell carcinoma, fibroepitheliomatous pattern - esp. reticulated SK.
Melanocytic nevus.
Condyloma acuminatum - may have horn cysts, more probable than SK in the genital area.
Inverted follicular keratosis - predominantly endophytic growth pattern, may be considered a variant of seborrheic keratosis.^[6]

Images

Seborrheic keratosis - low mag. (WC)
Seborrheic keratosis - high mag. (WC)

www:

Histologic subtypes

Like very common lesion, there are subtypes:^[5]

Acanthotic seborrheic keratosis - thickened stratum spinosum; thick epidermis.
Reticulated seborrheic keratosis - vaguely resembles fibroepithelioma of Pinkus (BCC, fibroepitheliomatous pattern).
Irritated seborrheic keratosis - spongiosis (epidermal intercellular edema) and inflammation.
Digitated seborrheic keratosis - papillomatous projections, architecture mimics a verruca.
Stucco keratosis - pointed papillomatous projections.

Sign out

SKIN LESION, MID BACK, BIOPSY:
- SEBORRHEIC KERATOSIS.

SKIN LESION, RIGHT SCAPULA, PUNCH BIOPSY:
- RETICULATED SEBORRHEIC KERATOSIS.

Micro

The sections show skin with acanthosis, pseudohorn cysts, parakeratosis, hyperkeratosis and focal basal epidermal pigmentation. There is no basal nuclear atypia, and there are no melanocytic nests or mitoses. There is minimal dermal inflammation. There is no apparent solar elastosis.

Without horn pseudocysts

The sections show skin with acanthosis, a thin layer of compact keratin and focal basal epidermal pigmentation. Dilated blood vessels surrounded by collagen are seen in the superficial dermis. No pseudohorn cysts are identified. A granular layer is present.

There is no basal nuclear atypia. There is no mitotic activity and no melanocytic nests. There is no solar elastosis. No koilocytes are apparent.

Minimal hyperkeratosis

The sections show skin with acanthosis, pseudohorn cysts, rare parakeratosis, minimal hyperkeratosis and focal basal epidermal pigmentation. There is no basal nuclear atypia, no appreciable mitotic activity and there are no melanocytic nests. There is minimal dermal inflammation. Solar elastosis is present.

Reticulated seborrheic keratosis

The sections show hair-bearing skin with fine strands of benign basaloid epidermal cells extending from the epidermis. The superficial dermis has dense collagen. No significant inflammation is present. Pseudohorn cysts are present focally.

There is no hyperkeratosis or acanthosis. No pigmentation is apparent. No large blood vessels are identified. No nuclear atypia is seen.

References

↑ URL: http://emedicine.medscape.com/article/1059477-overview#a0199. Accessed on: 26 August 2011.
↑ ^2.0 ^2.1 Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 595. ISBN 978-1416054542.
↑ URL: http://emedicine.medscape.com/article/1059477-overview. Accessed on: 26 August 2011.
↑ URL: http://www.healthcare.uiowa.edu/dermatology/dpt/HornCyst.htm. Accessed on: 13 September 2012.
↑ ^5.0 ^5.1 Busam, Klaus J. (2009). Dermatopathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Saunders. pp. 338-9. ISBN 978-0443066542.
↑ Busam, Klaus J. (2009). Dermatopathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Saunders. pp. 341. ISBN 978-0443066542.

[emed_sk2-1] URL: http://emedicine.medscape.com/article/1059477-overview#a0199. Accessed on: 26 August 2011.

[Ref_PCPBoD8_595-2] 2.0 ^2.1 Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 595. ISBN 978-1416054542.

[emed_sk1-3] URL: http://emedicine.medscape.com/article/1059477-overview. Accessed on: 26 August 2011.

[4] URL: http://www.healthcare.uiowa.edu/dermatology/dpt/HornCyst.htm. Accessed on: 13 September 2012.

[Ref_Derm338-9-5] 5.0 ^5.1 Busam, Klaus J. (2009). Dermatopathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Saunders. pp. 338-9. ISBN 978-0443066542.

[Ref_Derm341-6] Busam, Klaus J. (2009). Dermatopathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Saunders. pp. 341. ISBN 978-0443066542.

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