Seborrheic keratosis
Author:
Mikael Häggström [notes 1]
Gross appearance of a relatively large seborrheic keratosis.
Seborrheic keratosis, low magnification.
Seborrheic keratosis, high magnification.
Contents
Gross processing of skin excisions
| Lesion size | |||
|---|---|---|---|
| <4 mm | 4 - 8 mm | 9 - 15 mm | |
| Benign appearance |
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| Suspected malignancy | 
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In table above, each top image shows recommended lines for cutting out slices to be submitted for further processing. Bottom image shows which side of the slice that should be put to microtomy. Dashed lines here mean that either side could be used. Further information: Gross processing of skin excisions
Microscopic evaluation
Typical microscopic findings in seborrheic keratosis:
- A localized epidermal proliferation of basaloid and squamoid cells (mostly round and basaloid).[2]
- Most commonly a dome-shaped exophytic epidermal growth, containing multiple cornified cysts.[2]
- Melanin pigment deposition can occur.[2]
Squamous cell-like skin proliferations: Differential diagnosis
Main differential diagnoses and their characteristics:[3]
Invasive squamous-cell carcinoma of the skin: Atypical and pleomorphic keratinocytes, involving the dermis and the sub-cutis with a potential metastatic spread.
Squamous-cell carcinoma in situ (Bowen’s disease): Atypical keratinocytes at every layer of epidermis.
Actinic keratosis: Atypical keratinocytes that do not span the full thickness of the epidermis (or, in Bowenoid variant, are less disordered with less nuclear atypia and crowding).
Keratoacanthoma: Symmetrical and circumscribed proliferation of keratinocytes, with central horn plug, with epidermis that extends over the tumor. It can be regarded as a highly differentiated SCC.
Crush artifacts: Needles used to orient the skin sample may create crush artifacts (black arrow) mimicking cellular atypia with mainly hypereosinophilia and nuclear pleomorphism. Image also shows folding artifacts (white arrows).
Adnexal carcinomas: Squamous differentiation, but does not show connection with the epidermis and highlights adnexal features.
Adenosquamous carcinoma: Mixed glandular and squamous differentiation.
Verruca vulgaris: Marked hyperkeratosis and papillomatosis. Rete ridges slope inward at the borders of the lesion.
Verrucous squamous cell carcinoma[notes 3]: Exophytic squamous proliferation with marked papillomatosis and low atypia and the presence of koilocyte-like changes. Found in head and neck locations, as well as in the genitalia and sole of the foot.
Inverted follicular keratosis:[notes 4]: Sharply circumscribed endophytic verrucous proliferation with prominent squamous features.
Seborrheic keratosis: Acanthosis, absence of atypia, pseudo-horn cysts, in inflamed lesions, mitoses may be present.
Bowenoid papulosis: Atypical keratinocytes and mitoses. Histology similar to Bowen’s disease.
A melanoma may have relatively plentiful eosinophilic cytoplasm, and be seemingly continuous with the squamous epithelium (at left in image), thus resembling a squamous cell carcinoma. However, the nesting of cells at right in the image is more characteristic of a melanoma.
Metastasis: Personal medical history of the patient, nodular proliferation without connection to epidermis, immunohistochemical evaluation. Squamous-cell carcinoma metastasis from lungs to the skin is pictured.
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Clinically, seborrheic keratosis generally occurs in elderly patients.
Reporting
The most important component is generally whether there is any evidence of malignancy. Example:
 |
- See also: General notes on reporting
Notes
- ↑ For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.
- ↑ The excision examples show a normal mole (upper row, benign appearance) and a superficial basal cell carcinoma (lower row, suspected malignancy).
- ↑ - Buschke–Löwenstein tumor is an alternative name for verrucous squamous cell carcinoma in the ano-genital region.
- Carcinoma cuniculatum is a characteristic form of verrucous squamous cell carcinoma on the sole. - ↑ Inverted follicular keratosis is generally thought to be a rare variant of seborrheic keratosis, but this position is not universally accepted.
- Karadag, AyseSerap; Ozlu, Emin; Uzuncakmak, TugbaKevser; Akdeniz, Necmettin; Cobanoglu, Bengu; Oman, Berkant (2016). "Inverted follicular keratosis successfully treated with imiquimod ". Indian Dermatology Online Journal 7 (3): 177. doi:. ISSN 2229-5178.
Main page
References
- ↑ There are many variants for the processing of skin excisions. These examples use aspects from the following sources:
- . Handläggning av hudprover – provtagningsanvisningar, utskärningsprinciper och snittning (Handling of skin samples - sampling instructions, cutting principles and incision. Swedish Society of Pathology.
- For number of slices and coverage of lesions, depending on size. - Monica Dahlgren, Janne Malina, Anna Måsbäck, Otto Ljungberg. Stora utskärningen. KVAST (Swedish Society of Pathology). Retrieved on 2019-09-26.
- For slices towards the tips to determine radicality, which can be parallel to the slices through the lesions (shown), or as longitudinal slices that go through each tip. - . Dermatopathology Grossing Guidelines. University of California, Los Angeles. Retrieved on 2019-10-23.
- For microtomy of the most central side at the lesion - "The principles of mohs micrographic surgery for cutaneous neoplasia
- With a "standard histologic examination" that, in addition to the lesion, only includes one section from each side along the longest diameter of the specimen.
- It also shows an example of circular coverage, with equal coverage distance in all four directions.
- The entire specimen may be submitted if the risk of malignancy is high. - . Handläggning av hudprover – provtagningsanvisningar, utskärningsprinciper och snittning (Handling of skin samples - sampling instructions, cutting principles and incision. Swedish Society of Pathology.
- ↑ 2.0 2.1 2.2 Weidner, Noel (2009). Modern surgical pathology . Philadelphia, PA: Saunders/Elsevier. ISBN 978-1-4160-3966-2. OCLC 460883320.
- ↑ Initially copied from: Paolino, Giovanni; Donati, Michele; Didona, Dario; Mercuri, Santo; Cantisani, Carmen (2017). "Histology of Non-Melanoma Skin Cancers: An Update ". Biomedicines 5 (4): 71. doi:. ISSN 2227-9059. - "This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)."
