science

Seborrheic keratosis

Seborrheic keratosis is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Seborrheic keratosis rather than just read about it. In short: A seborrheic keratosis is a non-cancerous (benign) skin tumor that originates from cells, namely keratinocytes, in the outer layer of the skin called the epidermis. Like liver spots, seborrheic keratoses are seen more often as people age.

Key takeaways

Seborrheic keratosis belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Seborrheic keratosis to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Seborrheic keratosis from memory before moving on to harder problems.

Reference excerpt

A seborrheic keratosis is a non-cancerous (benign) skin tumor that originates from cells, namely keratinocytes, in the outer layer of the skin called the epidermis. Like liver spots, seborrheic keratoses are seen more often as people age. The tumors (also called lesions) appear in various colors, from light tan to black. They are round or oval, feel flat or slightly elevated, like the scab from a healing wound, and range in size from very small to more than 2.5 centimetres (1 in) across. They are often associated with other skin conditions, including basal cell carcinoma. Sometimes, seborrheic keratosis and basal cell carcinoma occur at the same location. At clinical examination, a differential diagnosis considers warts and melanomas. Because only the top layers of the epidermis are involved, seborrheic keratoses are often described as having a "pasted-on" appearance. Some dermatologists refer to seborrheic keratoses as "seborrheic warts", because they resemble warts, but strictly speaking, the term "warts" refers to lesions that are caused by the human papillomavirus.

Cause The cause of seborrheic keratosis is not known. The only definitive association is that its prevalence increases with age.

Diagnosis

Visual diagnosis is made by the "stuck on" appearance, horny pearls or cysts embedded in the structure. Darkly pigmented lesions can be challenging to distinguish from nodular melanomas. Furthermore, thin seborrheic keratoses on facial skin can be very difficult to differentiate from lentigo maligna even with dermatoscopy. Clinically, epidermal nevi are similar to seborrheic keratoses in appearance. Epidermal nevi are usually present at or near birth. Condylomas and warts can clinically resemble seborrheic keratoses, and dermatoscopy can be helpful to differentiate them. On the penis and genital skin, condylomas and seborrheic keratoses can be difficult to differentiate, even on biopsy. A study examining over 4,000 biopsied skin lesions identified clinically as seborrheic keratoses showed 3.1% were malignancies. Two-thirds of those were squamous cell carcinoma. To date, the gold standard in the diagnosis of seborrheic keratosis is represented by the histolopathologic analysis of a skin biopsy.

Subtypes Seborrheic keratoses may be divided into the following types:

Differential diagnoses Dermatosis papulosa nigra (DPN) is a condition of many small, benign skin lesions on the face, a condition generally presenting on darker-skinned individuals. DPN is extremely common, affecting up to 30% of black people in the United States.

Treatment Medical reasons for removing seborrheic keratoses include irritation and bleeding. They may also be removed for cosmetic reasons. Generally, lesions can be treated with electrodesiccation and curettage, or cryosurgery. When correctly performed, removal of seborrheic keratoses will not cause much visible scarring.

Epidemiology Seborrheic keratosis is the most common benign skin tumor. Incidence increases with age. There is less prevalence in people with darker skin. In large-cohort studies, all patients aged 50 and older had at least one seborrheic keratosis. Onset is usually in middle age, although they are common in younger patients too, as they are found in 12% of 15-year-olds to 25-year-olds, which makes the term "senile keratosis" a misnomer.

Illustrations

Worked examples

Example 1 — a first encounter with Seborrheic keratosis

Start with the simplest possible case. Write down what Seborrheic keratosis claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Seborrheic keratosis before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Seborrheic keratosis ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Seborrheic keratosis

In research: Seborrheic keratosis appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Seborrheic keratosis in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Seborrheic keratosis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dermal and subcutaneous growths, Epidermal nevi, neoplasms, and cysts, so understanding it makes those chapters shorter.
In everyday life: Look for Seborrheic keratosis outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Seborrheic keratosis in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Seborrheic keratosis means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Seborrheic keratosis out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Seborrheic keratosis in simple terms?

Why does Seborrheic keratosis matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Seborrheic keratosis?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Seborrheic keratosis.