Key Points

  • 1.

    Proliferation of keratinocytes or basal cells

  • 2.

    Scaling usually prominent

  • 3.

    Bleeding or crusting suggests cancer

Actinic Keratosis

Key Points

  • 1.

    Precancerous

  • 2.

    Prevent with sun protection

Definition

Actinic (solar) keratosis is a precancerous neoplasm of the epidermis caused by the ultraviolet (UV) portion of sunlight. The abnormal keratinocytes in actinic keratoses are confined to the epidermis and constitute a premalignant change. The proliferation of these abnormal cells is clinically manifest as a rough, scaling patch or papule ( Fig. 5.1 ).

Although considered premalignant, most actinic keratoses do not progress to skin cancer.

Table 5.1
Epidermal Growths
Frequency (%) a Etiology Physical Examination Differential Diagnosis Laboratory Test (Biopsy)
Actinic keratosis 1.7 Sunlight Ill-marginated, reddish, rough, scaling patch or papule Squamous cell carcinoma
Seborrheic keratosis
Superficial basal cell carcinoma
Lichenoid keratosis
When thick scale or indurated base
Basal cell carcinoma 1.7 Sunlight Yes
Nodular Pearly nodule with telangiectasia, often has central depression or ulcer Molluscum contagiosum
Squamous cell carcinoma
Sebaceous hyperplasia
Nevus
Merkel cell carcinoma
Trichoepithelioma
Pigmented Blue-black plaque or nodule with pearly border Malignant melanoma
Nevus
Seborrheic keratosis
Superficial Red, scaling, crusted eczematous appearing patch Psoriasis
Eczema
Bowen’s disease
Lichenoid keratosis
Sclerosing Whitish, slightly depressed, sometimes crusted pink plaque/patch Squamous cell carcinoma
Non-healing scar
Corn 0.4 Friction Hyperkeratotic papule or nodule with compact clear core Wart No
Molluscum contagiosum 0.3 Poxvirus Translucent papule with umbilicated center Comedo
Nodular basal cell carcinoma
No
Seborrheic keratosis 1.6 Tan-brown, greasy, pasted-on papule or plaque Wart
Actinic keratosis
Nevus
Malignant melanoma
Pigmented basal cell carcinoma
No
Skin tag 0.5 Soft, skin-colored, pedunculated papule Neurofibroma nevus No
Squamous cell carcinoma 0.2 Sunlight
Viruses
Chemicals
Flesh-colored, hard, crusted or scaling nodule, often ulcerated Keratoacanthoma
Basal cell carcinoma
Wart
Lichenoid keratosis
Actinic keratosis
Merkel cell carcinoma
Trichoepithelioma
Nevus sebaceous
Yes
Wart 5.2 Papillomavirus No
Common Flesh-colored, scaling, vegetative papule or nodule, skin lines interrupted, studded with black puncta Corn
Squamous cell carcinoma
Flat Reddish, smooth, flat, well-demarcated papule Lichen planus
Comedo
Corn
Plantar Solitary, grouped or mosaic scaling papules, skin lines interrupted, studded with black puncta Squamous cell carcinoma
Genital Soft, moist, cauliflower-appearing papules or nodule Squamous cell carcinoma
Secondary syphilis
No

a Percentage of new dermatology patients with this diagnosis seen in the Hershey Medical Center Dermatology Clinic, Hershey, PA.

Figure 5.1, Actinic keratosis. A. Rough, scaling, ill-marginated, pinkish patches and papules on markedly sun-damaged skin (arrows). B. Epidermis – atypical keratinocytes in lower epidermis. Dermis – chronic inflammation.

Incidence

The incidence of actinic keratoses varies with (1) skin pigmentation; (2) geographic location; and (3) amount of sun exposure. Thus, the incidence of actinic keratoses is high in Caucasians who have light skin, live in the southern United States where there is an abundance of natural sunlight, and engage in frequent outdoor activity. In the authors’ clinic, 1.7% of new patients were seen because of actinic keratoses, although the incidence would be higher in the “Sunbelt.” Moreover, in many patients, actinic keratoses are an incidental finding.

Light skin and abundant sun exposure may result in actinic keratoses.

History

Risk factors can usually be elicited in the history. The patient may have a genetic predisposition. Fair-skinned Caucasians have the least amount of protective pigment. A family history of skin cancer or an Irish or Anglo-Saxon heritage is frequently obtained. Second, the geographic location where the patient has lived directly influences the amount of UV light exposure. As one moves toward the equator, the UV light intensity increases dramatically. Last, the occupational and recreational activities of the patient with reference to sun exposure provide another clue. Farmers, sailors, and others with occupations that require working outdoors have a high amount of UV light exposure. Similarly, persons who spend many hours at the poolside or on the beach are at higher risk.

Physical examination

Actinic keratoses are 1 to 10 mm, reddish, ill-marginated patches and papules that have a rough, yellowish brown, adherent scale. Their ill-defined margins make them indistinct to the casual observer. Their rough-textured surface is often easier to feel than to see. Actinic keratoses occur in sun-exposed areas: the face, dorsum of the hands and forearms, neck, upper back, chest, and lower legs. They generally are found on UV-damaged skin that has a yellowish hue, wrinkles, and freckled pigmentation.

An actinic keratosis is rough, scaling, and ill marginated; it is often easier felt than seen.

Differential diagnosis

An actinic keratosis must be differentiated from other epidermal tumors. Most often, it is confused with a seborrheic keratosis . The well-demarcated, “pasted on” appearance of a seborrheic keratosis differentiates it from an actinic keratosis. In situ squamous cell carcinoma is a larger plaque with margins that are well defined, in contrast to the margins of an actinic keratosis. Hypertrophic or indurated actinic keratosis ( Fig. 5.1 ) cannot be differentiated with certainty from squamous cell carcinoma and should undergo biopsy. Superficial basal cell carcinoma , which resembles is situ squamous cell carcinoma clinically, is occasionally confused with actinic keratosis. Lichenoid keratosis should also be considered in the differential diagnosis. A lichenoid keratosis is an inflamed lentigo or thin seborrheic keratosis which is well-demarcated with some residual tan/brown coloration within the pink inflamed lesion.

Differential Diagnosis of Actinic Keratosis

  • Seborrheic keratosis

  • Squamous cell carcinoma

  • Superficial basal cell carcinoma

  • Lichenoid keratosis

Laboratory and biopsy

Actinic keratosis is characterized histologically by a partial-thickness dysplasia of the epidermis ( Fig. 5.1B ). A hyperkeratosis with underlying irregular hyperplasia of mildly dysplastic keratinocytes is seen. A chronic inflammatory response is present in the dermis. All thick and indurated actinic keratoses should undergo biopsy to rule out squamous cell carcinoma, as well as lesions that have not responded to previous treatment.

Indurated and therapeutically unresponsive actinic keratoses should undergo biopsy to rule out carcinoma.

Therapy

Prevention by reducing sunlight exposure is the most effective form of therapy. Patients who are sensitive to the sun or have developed actinic keratoses should wear protective clothing such as broad-brimmed hats and long-sleeved shirts when outside. Sunscreens with a sun protective factor (SPF) of 30 should be used on exposed skin. The regular use of sunscreens prevents the development of new actinic keratoses, as well as hastening the resolution of those that already exist. Avoidance of sun exposure at midday (from 10:00 a.m. to 2:00 p.m.), when UV radiant energy is most intense, is recommended. Patient awareness and education should begin in childhood.

Use sun protection to prevent more actinic damage.

Cryosurgery with liquid nitrogen is the most common treatment for actinic keratoses and is most useful when a few lesions are present. Thick, hypertrophic, actinic keratoses are also better treated in this way. Freezing can be accomplished in a manner similar to that described for warts.

Avoid overzealous treatment of thin actinic keratoses because of possible scarring.

Topical chemotherapy with 5-fluorouracil cream 5% (Efudex) is the most common means of treating multiple actinic keratoses. 5-Fluorouracil inhibits DNA synthesis by blocking the enzyme thymidylate synthase. When 5-fluorouracil is applied to normal skin, little reaction occurs, but when it is applied to sun-damaged skin, those areas with actinic keratoses become inflamed. The medication is applied to the involved areas twice daily. Erythema develops within several days. Subsequently, within 2 to 4 weeks, the actinic keratoses become painful, crusted, and eroded, at which time the medication is stopped. Patients need to be warned about the discomfort and cosmetically unsightly effects of 5-fluorouracil, which are temporary and resolve after discontinuing treatment. Because of the marked amount of inflammation that can occur, small regions may be treated at a time in patients with extensive actinic keratoses. A few patients may become allergic to 5-fluorouracil. Patients with severe actinic damage can be expected to require treatment every couple of years. Alternative agents include (1) diclofenac gel 3% (Solaraze), a nonsteroidal antiinflammatory drug (NSAID), applied twice daily for 3 months; (2) imiquimod cream 5% (Aldara), a topical immune response modifier, applied twice weekly for 4 months; (3) ingenol mebutate 0.015% gel applied daily to the face/scalp for 3 days and 0.05% gel applied daily to the extremities/trunk for 2 days respectively; and (4) photodynamic therapy, chemical peel, or laser.

Therapy for Actinic Keratosis

Prevention

  • Sunscreen ≥ SPF 30

  • Broad-brimmed hat, long-sleeved shirt, and pants

  • Avoidance of intense midday sun (from 10:00 a.m. to 2:00 p.m.)

Initial

  • Cryotherapy with liquid nitrogen

Alternative

  • 5-Fluorouracil 5% cream twice daily for 2–3 weeks

  • Diclofenac 3% gel twice daily for 3 months

  • Imiquimod 5% cream twice weekly for 16 weeks

  • Ingenol mebutate 0.015% or 0.05% gel applied daily to the face or extremities/trunk for 3 or 2 days, respectively

  • Photodynamic therapy, chemical peel, or laser

Course and complications

In patients with chronically sun-damaged skin, the acquisition of more actinic keratoses can be expected. Some actinic keratoses spontaneously disappear (up to 26%), although others may develop into squamous cell carcinoma. The number that do develop into squamous cell carcinoma appears to be small, less than 1 in 1000 within 1 year. Metastases from squamous cell carcinomas arising in actinic keratoses are very uncommon.

Actinic keratosis has a small potential of developing into a squamous cell carcinoma.

Pathogenesis

Actinic keratoses are produced by UV radiation-induced damage to keratinocyte DNA. This results in unrepaired or error-prone repaired DNA. Abnormal replication occurs and results in epidermal cellular hyperplasia. The cells within an actinic keratosis are arranged in a disorderly way and have increased mitoses and an abnormal chromatin pattern. Other precancerous keratinocytic neoplasms similar to actinic keratoses are caused by artificial UV light, X-irradiation, or polycyclic aromatic hydrocarbons.

Basal Cell Carcinoma

Key Points

  • 1.

    Malignancy of the epidermal basal cell

  • 2.

    Very rarely metastasizes

  • 3.

    Different types have different appearances

Definition

Basal cell carcinoma is a malignant neoplasm arising from the basal cells of the epidermis. Although these cancers rarely metastasize, their potential for local destruction attests to their malignant nature. UV radiation is the cause of most basal cell carcinomas in humans. Four clinically and histopathologically distinct types of basal cell carcinoma are recognized: nodular, pigmented, superficial, and scarring (sclerotic).

Incidence

Basal cell carcinoma is the most common human malignant disease; it affects more than 2 million persons annually in the United States. Of the new patients in the authors’ clinic 2% are seen for basal cell carcinoma. The increased frequency in adult Caucasians is related to sun exposure.

Basal cell carcinoma is the most common skin cancer, but it very rarely metastasizes.

History

The patient with basal cell carcinoma seeks medical attention because of a new growth, especially if it is a nonhealing, easily bleeding lesion. There may be a personal or family history of skin cancer. The risk of basal cell carcinoma is higher in patients with light skin, in those who live in southern latitudes, and in those who work or play outdoors. Frequently, these patients have a history of sunburning easily and tanning poorly.

Physical Examination

The usual patient with basal cell carcinoma has fair skin, blue eyes, blonde or red hair, and actinic-damaged skin manifested by freckles, yellow wrinkling, and actinic keratoses. Basal cell carcinoma occurs in sun-exposed skin, particularly the head and neck.

A “pearly” appearance is the most characteristic feature of a nodular basal cell carcinoma.

The nodular type ( Fig. 5.2 ) of basal cell carcinoma is the most common. It is a “pearly,” semi-translucent papule or nodule that often has a central depression or crater, telangiectasia, and a rolled, waxy border. Ulceration and crusting can occur. Nodular basal cell carcinoma occurs most frequently on the face, especially the nose.

Types of basal cell carcinoma:

  • 1.

    Nodular

  • 2.

    Pigmented

  • 3.

    Superficial

  • 4.

    Scarring (sclerotic)

Figure 5.2, A. Nodular basal cell carcinoma. B. Basal cell carcinoma. Epidermis – thickened. Dermis – invasive buds and lobules of basaloid cells. C. Basal cell nevus syndrome – multiple pearly to flesh-colored papules and nodules with rolled border and telangiectasia and some crusting.

Pigmented basal cell carcinoma ( Fig. 5.3 ) is a shiny, blue–black papule, nodule, or plaque. The pigment is often speckled, and a pearly, rolled margin can be seen when the tumor is viewed from the side.

Figure 5.3, Pigmented basal cell carcinoma – black, slightly scaling, translucent plaque.

Superficial basal cell carcinoma ( Fig. 5.4 ) occurs most frequently on the thorax. It is a red, slightly scaling, well-demarcated, eczematous appearing patch. Centrally, it may become slightly eroded and crusted, subsequently leaving an atrophic, slightly depressed center. Its shape is oval to round, with a characteristic thread-like, pearly, rolled border. It is often referred to as multicentric superficial basal cell carcinoma because it skips islands of normal skin, similar to the way a forest fire may surround a stand of trees yet leave it unburned.

Figure 5.4, Superficial basal cell carcinoma – red, slightly scaling and crusted patch.

The scarring (sclerotic or morpheaform) basal cell carcinoma ( Fig. 5.5 ) is an atrophic, white, slightly eroded, or crusted plaque that often looks like a scar. It is frequently depressed and is the least common and most aggressive type of basal cell carcinoma.

Figure 5.5, Scarring basal cell carcinoma – pink, atrophic white, slightly crusted, ill-marginated patch.

Differential Diagnosis

Nodular basal cell carcinoma and sebaceous hyperplasia are sometimes difficult to differentiate clinically. Sebaceous hyperplasia is the proliferation of sebaceous glands surrounding a hair follicle that appears as a 1- to 3-mm, yellowish papule with overlying telangiectasia and a central pore. The yellowish coloration and central pore help to differentiate it from a basal cell carcinoma. Other epithelial growths that resemble a nodular basal cell carcinoma include a nonpigmented nevus , molluscum contagiosum , Merkel cell carcinoma, trichoepithelioma, fibrous papule of the nose, lichenoid keratosis, and squamous cell carcinoma .

Pigmented basal cell carcinoma can be confused with a seborrheic keratosis , pigmented nevus , and, most importantly, malignant melanoma . The pearly, rolled border of pigmented basal cell carcinoma helps to differentiate it from a malignant melanoma. If doubt exists, an excisional or deep shave biopsy should be performed.

Superficial basal cell carcinoma resembles a patch of dermatitis . It can be confused with psoriasis , nummular dermatitis , and squamous cell carcinoma . A persistent solitary lesion and lack of response to topical steroids clinically differentiate superficial basal cell carcinoma from dermatitis or psoriasis. A skin biopsy is the only way to differentiate it from squamous cell carcinoma in situ .

Any nonhealing scar-like lesions should undergo biopsy to rule out a scarring basal cell carcinoma.

Differential Diagnosis of Basal Cell Carcinoma

Nodular

    • Sebaceous hyperplasia

    • Flesh-colored nevus

    • Molluscum contagiosum

    • Merkel cell carcinoma

    • Trichoepithelioma

    • Fibrous papule of the nose

    • Squamous cell carcinoma

Pigmented

    • Seborrheic keratosis

    • Pigmented nevus

    • Malignant melanoma

Superficial

    • Dermatitis

    • Lichenoid keratosis

    • Squamous cell carcinoma

Scarring

    • Scar

Laboratory and Biopsy

The diagnosis of basal cell carcinoma should be confirmed by a shave or punch biopsy. The technique of skin biopsy is reviewed in Chapter 4 . The tumors are made up of uniform cells that resemble the basal layers of the epidermis (see Fig. 5.2B ). They have a uniform, large, oval, blue nucleus with indistinct cytoplasm. The tumor extends from the epidermis into the dermis as nodular or cystic structures, bands, or strands, or as buds from the epidermis. The nodular areas have peripheral palisading with retraction from the surrounding stroma. The cells in some basal cell carcinomas have a “squamoid” appearance, which makes them difficult to differentiate from squamous cell carcinoma. The infiltrative, morpheaform, micronodular, and mixed histologic subtypes of primary basal cell carcinoma are more aggressive and more difficult to eradicate.

A chronic eczematous patch or nonhealing crusted lesion should be biopsied to rule out a superficial basal cell carcinoma.

Therapy

Treatment of basal cell carcinoma should be individualized according to the location of the lesion, the histopathologic type, the age of the patient, the general health of the patient, the size of the basal cell carcinoma, and whether it is primary or recurrent. Recurrence of basal cell carcinoma is related particularly to location on the nose or ear, size more than 2 cm, and histologic pattern of micronodular, infiltrative, and morpheic types. Treatment modalities include scalpel excision, curettage and electrodesiccation, radiotherapy, cryotherapy, and topical 5-fluorouracil or imiquimod. Each treatment must be properly selected to achieve a high cure rate. Surgical modalities are those most frequently used and have the best cure rates. The surgical techniques are reviewed in Chapter 4 .

Excision with primary suture closure, the most frequently used form of therapy, allows for histologic assessment of surgical margins. When the wound is large, grafts or tissue transposition flaps may be used to achieve closure. Excision is good for most basal cell carcinomas, but is the treatment of choice for large basal cell carcinomas, recurrent tumors, sclerosing types of basal cell carcinoma, basal cell carcinomas at sites of high recurrence such as the nose or ear, and basal cell carcinoma that extends into the subcutaneous tissue. A specialized form of excision using detailed mapping of the extent of the tumor with histologic orientation is the Mohs micrographic surgical technique . This meticulous procedure is most often used for basal cell carcinomas on the head and neck, recurrent basal cell carcinoma, and primary tumors with a high risk of recurrence.

Mohs micrographic surgery has the highest cure rate and preserves the most normal skin. It is indicated for most facial/neck basal cell carcinomas and for recurrent basal cell carcinomas.

Curettage and electrodesiccation is a therapeutic modality frequently used by dermatologists. The clinical margins of the tumor are defined by vigorous curettage until the firm, fibrous consistency of normal dermis is felt. This is followed by electrodesiccation. The entire procedure of curettage and electrodesiccation may be repeated to ensure removal of the tumor. The resultant wound heals by secondary intention over a 2- to 3-week period, with excellent cosmetic results in most cases. Experience is needed to obtain good cure rates. Curettage and electrodesiccation should not be used for basal cell carcinomas with poorly defined clinical borders, for sclerosing basal cell carcinomas, for recurrent basal cell carcinomas, or in certain anatomic locations such as the nasolabial fold, and eyelids.

Radiation therapy is reserved for elderly patients because the subsequent chronic radiodermatitis that occurs years after the therapy may be cosmetically unacceptable, and because of the potential for developing a new primary cancer in the radiotherapy site. Radiation therapy is used when the patient refuses surgical treatment or has a large tumor that would be difficult to treat surgically.

Cryosurgery with liquid nitrogen is reserved for those clinicians experienced in its use for cancer therapy. The margins and depth of the tumor must be estimated clinically. Cryoprobes are used to monitor the depth of the freeze. After surgery, marked tissue reaction occurs with edema, tissue necrosis, weeping, and crusting.

Topical chemotherapy with 5-fluorouracil or imiquimod is, in general, inappropriate for treating skin cancer. It should not be used on deep or recurrent tumors. It is occasionally used in patients who have multiple, superficial, multicentric basal cell carcinomas that otherwise would require numerous surgical procedures. Treatment is continued for weeks until marked inflammation and erosion occur. Residual areas suspected to have tumor must undergo biopsy, and another therapeutic modality must be used if basal cell carcinoma persists.

Vismodegib and sonidegib are hedgehog pathway inhibitors targeting smoothened. They are indicated in the treatment of locally advanced, multiple, or metastatic basal cell carcinoma. Serious adverse side-effects including birth defects limit their use.

Prevention of further sun-induced damage to the skin is mandatory. Sun protection includes the regular use of sunscreens with an SPF of 15 to 30, protective clothing (wide-brimmed hat and long-sleeved shirt), and avoidance of midday sun (from 10 a.m. to 2 p.m.).

Prevention with sun protection – sunscreen, clothing, and avoid midday sun.

Therapy for Basal Cell Carcinoma

Prevention

  • Sunscreen ≥ SPF 30

  • Broad-brimmed hat, long-sleeved shirt, and pants

  • Avoidance of intense midday sun (from 10:00 a.m. to 2:00 p.m.)

Initial

  • Excision

  • Curettage and electrodesiccation

  • Mohs micrographic surgery

Alternative

  • Radiation

  • Cryotherapy

  • 5-Fluorouracil or imiquimod topically for multiple superficial basal cell carcinomas

  • Vismodegib, sonidegib

Course and Complications

Because its course is frequently indolent, a basal cell carcinoma is often ignored. It may enlarge locally and can invade underlying tissues, resulting in significant morbidity and mutilation. Vital structures, such as an eye, a nose, or an ear, may be totally lost.

Basal cell cancer rarely metastasizes, presumably because of stromal dependence. The metastatic rate is estimated to be less than 0.003% (1 in 52,000 cases in one series). The excessively large, ulcerated, locally destructive, and recurrent basal cell carcinoma is most likely to metastasize. Regional lymph nodes, lung, and bone are the most likely tissues involved. Routine follow-up every 12 months of patients with basal cell carcinoma is recommended because 35% of these patients will develop another basal cell carcinoma within 5 years.

Pathogenesis

The most common factor related to the development of basal cell carcinoma is UV radiation. Other factors to be considered are arsenic ingestion, genetic predisposition, X-irradiation, and chronic irritation. Mutations of the genes, smoothened (SMO) and patched (PTCH), in the hedgehog pathway are implicated in over 90% of basal cell carcinomas, and the basal cell nevus syndrome. The basal cell nevus syndrome is a rare autosomal-dominant disorder characterized by early development of multiple basal cell carcinomas ( Fig. 5.2C ), jaw cysts, macrocephaly, palmar and plantar pits, increased risk of medulloblastoma, and other congenital abnormalities. The origin of basal cell carcinoma is a pluripotential primordial epithelial cell in the basal layer of the skin or, less often, a cutaneous appendage such as the hair follicle.

Corns

Key Points

  • 1.

    Caused by pressure or friction

  • 2.

    Do not interrupt skin lines

Definition

A corn is a localized thickening of epidermis secondary to chronic pressure or friction. It occurs most often on the feet. Synonyms are clavus and heloma .

Incidence

Corns are extremely common. Many patients treat themselves or see a podiatrist rather than a physician.

History

The patient seeks medical care because of painful feet when standing or walking. A history of ill-fitting footwear or foot injury may be obtained.

Physical Examination

Corns are white-gray or yellow-brown, well circumscribed, horny papules or nodules. Paring the surface with a scalpel reveals a translucent core with preservation of skin lines. Hard corns occur on the sole ( Fig. 5.6 ) and external surface of the toes, where drying occurs. Soft corns occur between the toes, where sweating results in maceration.

Corns have a clear center and intact skin lines.

Figure 5.6, Corn. A. Thick, yellowish plaque with intact skin lines and compressed keratin center. B. Epidermis – thickened, with hyperkeratosis.

Differential Diagnosis

Plantar warts and corns are commonly confused. The simple maneuver of paring the surface and identifying the presence of skin lines with a translucent core confirms that the lesion is a corn.

Differential Diagnosis of a Corn

  • Wart

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