Epidermal Growths

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.

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.

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.

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.

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.

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.

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 .

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.

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.

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.).

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.

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.

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.