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Dermatology
Actinic Keratosis, Basal Cell Carcinoma, and Squamous Cell Carcinoma
Built from Dermatology, 5th Edition
What’s inside
13 sections · 167 slides
Overview
- What this topic covers
- #1
- Key terms up front
History and Epidemiology
How these cancers were first recognized, and how common they are today.
- Early recognition of skin cancer
- How common is keratinocyte carcinoma
- Sunlight dose (UV radiation) tracks closely with skin cancer rates across cities.
- Latitude, age, and lifetime risk
- Incidence of both BCC and SCC climbs steadily with age in this population data.
- How common are actinic keratoses
- Squamous cell carcinoma epidemiology
- Basal cell carcinoma epidemiology
- NMSC mortality trends
- Skin pigmentation and skin cancer risk
- Why skin pigmentation matters so much
Risk Factors
Ultraviolet exposure dominates, but chemicals, viruses, immune status, and genes all contribute.
- What raises the risk of keratinocyte carcinoma
- Ultraviolet radiation: the dominant cause
- Two exposure patterns, two cancers
- Indoor tanning and therapeutic UV light
- Ionizing radiation and occupational exposure
- Environmental and clinical risk factors for BCC and cSCC
- Environmental and clinical risk factors for BCC and cSCC (continued)
- Environmental and clinical risk factors for BCC and cSCC (continued)
- Chemical and arsenic exposure
- Human papillomavirus (HPV) infection
- Organ transplantation and immunosuppression
- Reducing risk in transplant patients
- Drugs, HIV, and other exposures
- Genetic predisposition to skin cancer
- Xeroderma pigmentosum and oculocutaneous albinism
- Epidermodysplasia verruciformis and dystrophic EB
- Basal cell nevus syndrome (BCNS)
- A patient with basal cell nevus syndrome (BCNS) can develop many BCCs, from tiny to over 5 cm.
- This patient has three superficial BCCs and one large nodular BCC on the chest.
- BCNS causes recognizable facial and skeletal features beyond the skin tumors.
- Diagnostic criteria for basal cell nevus syndrome
- Other rare BCC-prone genetic syndromes
- Repeat cancers and field cancerization
- This diagram traces how UV light slowly turns a normal keratinocyte into a metastatic SCC.
Actinic Keratosis: Clinical Features
A rough, scaly sun spot that is a marker — and sometimes a precursor — of squamous cell cancer.
- What is an actinic keratosis
- Actinic keratosis clinical spectrum
- Examining and classifying AKs
- Hypertrophic AKs are thick, scaly plaques — easy to see and often bother patients because of their bulk.
- Pigmented AKs lack the redness of typical AKs and instead look brown and reticulated (net-like).
- Lichenoid and atrophic AK
- Actinic cheilitis is the AK equivalent on the lower lip — the site that gets the most direct sun exposure.
- A second example of actinic cheilitis: erosions, scaling, and white patches across the lower lip.
Squamous Cell Carcinoma: Clinical Features
From in-situ Bowen disease to invasive cSCC, keratoacanthoma, and verrucous carcinoma.
- Squamous cell carcinoma in situ (Bowen disease)
- Bowen disease — clinical spectrum
- Telling Bowen disease apart from its mimics
- This is another example of Bowen disease: a pink plaque with white scale and a hemorrhagic crust on sun-damaged skin.
- This cutaneous horn arose from an SCC in situ on the ear helix (rim).
- SCC in situ can also affect the nail unit, shown here as hyperkeratosis and hemorrhagic crusting.
- Pigmented SCC in situ can look clinically like a melanoma — brown-to-black rather than the usual pink or red.
- Erythroplasia of Queyrat is the name given to SCC in situ on the glans penis.
- Other variants of SCC in situ
- Invasive cutaneous squamous cell carcinoma
- Invasive cSCC — clinical spectrum
- cSCC of the lower lip: extensive thick scale and white patches (leukoplakia) across the vermilion lip.
- A supraorbital (above the eyebrow) SCC: a large keratotic nodule set against visibly wrinkled, sun-damaged skin.
- Panel A: a smooth erythematous nodule in front of the ear (preauricular area).
- This SCC of the lower lip proved fatal — the patient died from metastatic disease.
- Immunosuppressed transplant recipients are especially prone to recurrent cSCC after treatment.
- Staging invasive cSCC — how doctors size up risk
- TNM staging of head and neck cSCC
- TNM staging of head and neck cSCC (continued)
- cSCC overall stage grouping (from T, N, M)
- High-risk features of cutaneous SCC
- Keratoacanthoma: cancer or pseudo-cancer?
- Keratoacanthoma — clinical spectrum
- Keratoacanthoma variants
- Two more examples of the classic rapidly-growing, crater-shaped KA with a rolled border and keratin-filled core.
- A giant keratoacanthoma: yellow-red color and a clear history of rapid growth.
- Generalized eruptive keratoacanthomas (Grzybowski type): hundreds of small papules erupt over the body at once.
- Verrucous carcinoma
- Panel A: a large, longstanding nodule on the sole with a rabbit-burrow appearance (epithelioma cuniculatum).
- The Buschke-Lowenstein tumor is the genital subtype of verrucous carcinoma — a giant, cauliflower-like growth.
- A rare tumor that looks under the microscope like a nasopharyngeal cancer usually caused by Epstein-Barr virus (EBV).
- Imaging tools: dermoscopy and confocal microscopy
Actinic Keratosis and SCC: Pathology
What the tumor looks like under the microscope, from early AK to invasive, metastasizing SCC.
- This progression figure shows, side by side, three stages of the same disease process.
- Under the microscope, an AK shows abnormal, disordered keratinocytes mainly in the basal (deepest) layer.
- SCC in situ (Bowen disease) shows abnormal cells filling the FULL thickness of the epidermis.
- Invasive SCC: from well to poorly differentiated
- Invasive SCC — range of histopathology
- How thickness predicts spread and recurrence
- A keratoacanthoma has a distinctive "volcano-like" shape under low-power magnification.
- Verrucous carcinoma shows marked, irregular thickening of the epidermis with prominent hyperkeratosis.
- Lesions that mimic SCC under the microscope
- Rare tumors that can mimic invasive SCC
Basal Cell Carcinoma: Clinical Features
The most common human cancer, with four major clinical patterns.
- Basal cell carcinoma: general features
- Four major clinical types of BCC
- Nodular basal cell carcinoma
- Nodular basal cell carcinoma — clinical spectrum
- Not every BCC is dramatic — this photo shows subtle papules of BCC along the eyelid margin.
- Superficial basal cell carcinoma
- Panel A: numerous red patches and thin plaques on the back of a man with a history of arsenic exposure.
- Another superficial BCC — an erythematous plaque that can easily be mistaken for dermatitis.
- Morpheaform basal cell carcinoma
- Morpheaform basal cell carcinoma
- Fibroepithelial BCC (fibroepithelioma of Pinkus)
- Panels A and B: pigmented nodular BCCs with varying amounts of melanin, which can mimic melanoma clinically.
- Pigmented BCC: an admixture of scale and hemorrhagic crust centrally, with a translucent black rolled border superiorly.
- Two more examples of fibroepithelioma of Pinkus: soft, skin-colored to light pink, sessile plaques on the lower back.
- A second fibroepithelioma of Pinkus: a soft, skin-colored, sessile plaque on the lower back.
- Imaging BCC: dermoscopy and confocal microscopy
- Dermoscopy of a nodular BCC above the eyebrow shows telangiectatic (branching) vessels, redness, and cystic spaces.
- Reflectance confocal microscopy (RCM) images BCC almost at histology-level resolution, without a biopsy.
- Dermoscopy of pigmented "nevoid" BCCs on the abdomen in a patient with basal cell nevus syndrome.
Basal Cell Carcinoma: Pathology
Basaloid cells, stromal retraction clefts, and the histologic features behind each clinical subtype.
- What all basal cell carcinomas share
- Nodular, cystic, and micronodular BCC
- Superficial, pigmented, and infiltrative BCC
- Fibroepithelial and infundibulocystic BCC
- BCC — the range of histopathologic patterns
- Basosquamous and micronodular BCC — the aggressive forms
- Clear cell BCC is a histologic variant showing pronounced clear-cell change within the basaloid tumor clusters.
- Look-alikes of basal cell carcinoma under the microscope
- Look-alikes of basal cell carcinoma under the microscope (continued)
- The many named histopathologic patterns of nodular BCC
- The many named histopathologic patterns of nodular BCC (continued)
- Why this many names for one tumor
Evaluation and Risk Stratification
History, exam, biopsy, and sorting each tumor into a low- or high-risk category before treatment.
- Taking the history
- The physical examination
- Biopsy technique and pathology reporting
- Low-risk versus high-risk features for recurrence of NMSC
- Low-risk versus high-risk features for recurrence of NMSC (continued)
- Face, hands, and feet carry the highest recurrence risk
Surgical and Destructive Treatment
Excision, curettage, Mohs micrographic surgery, radiation, cryosurgery, and photodynamic therapy.
- Standard surgical excision
- Curettage: alone or with electrodesiccation
- Mohs micrographic surgery
- Radiation therapy
- Cryosurgery, PDT, and laser
Topical and Field-Directed Treatment
Treating one visible spot versus treating the whole sun-damaged field.
- Two treatment strategies for AKs
- Lesion-targeted treatments for actinic keratoses
- Topical field treatments for actinic keratoses
- 5-fluorouracil, diclofenac, and imiquimod
- Tirbanibulin and drugs in development
- Procedural field treatments for actinic keratoses
- Combining treatments and chemowraps
- Intralesional (injected) 5-fluorouracil and methotrexate
- Injecting drugs directly into a tumor
Systemic Therapy for Advanced Disease
Immune checkpoint inhibitors for advanced cSCC, and hedgehog pathway inhibitors for advanced BCC.
- When tumors need systemic (whole-body) treatment
- Immune checkpoint inhibitors for advanced cSCC
- Second-line options for advanced cSCC
- The hedgehog signaling pathway in BCC
- The hedgehog signaling pathway
- Vismodegib and sonidegib for advanced BCC
- This patient had a large, ulcerated tumor of the central chest — a locally advanced BCC too extensive for standard surgery.
- Common side effects of vismodegib and sonidegib
- Important: both drugs can cause birth defects
- Immune checkpoint inhibitors for advanced BCC
Prevention
Chemoprevention drugs, reducing immunosuppression, and sun-protection programs.
- Chemoprevention in high-risk patients
- Reducing immunosuppression and primary prevention
- Key takeaways
- Clinical bottom line
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- Dermatology, 5th Edition (2-Volume Set)