Intact skin is composed of epidermis and dermis. These act as physiologic barriers to infection and malignant spread. SCC and melanoma develop from different epidermal layers.

The typical SCC lesion is a firm, scaly papule or nodule containing a central ulcer surrounded by an indurated raised border (FIG 1).

Risk factors include the following:

Immune compromise (organ transplantation and AIDS)

Major risks for melanoma include the following:

SCC is the second most common type, behind basal cell carcinoma (BCC).

The American Cancer Society estimates more than 1 million new diagnoses of cutaneous BCC and SCC are made annually. However, BCC and SCC account for less than 0.1% of patient deaths caused by all cancers.

The American Cancer Society anticipates approximately 60,000 new melanoma cases each year, with an estimated 8110 deaths.

The probability of developing melanoma from birth to death is 2.04 (1 in 49) in males and 1.38 (1 in 73) in females.

Nail matrix SCC or melanoma account for less than 1% of their respective cutaneous malignancies. The histologic features of the epidermis and dermis, including physiologic barriers, are absent in the nail complex. In the nail complex, the matrix is adherent to the underlying phalanx.

Patients typically present for evaluation after noting the recent appearance of, or changes to, an existing lesion.

Change in size, shape, coloration, the presence of satellite lesions, or ulceration of a lesion should prompt a thorough evaluation and possible biopsy with histopathologic analysis (FIG 2).

Melanoma and SCC can metastasize. Regional lymph node beds (axillary) should be routinely examined in all suspected cases of upper extremity skin cancer.

The presence of a Hutchinson sign (extension of brown-black pigment from the nail bed, matrix, or nail plate onto the adjacent cuticle and proximal or lateral nail folds) is consistent with a subungual melanoma (FIG 3). Subungual melanoma should also be suspected when the nail bed contains a new or enlarging pigmented streak wider than 3 mm (FIG 4).

Although there have been reports of amelanotic melanoma of the nail bed, the actual incidence is unknown.

Radiographic evaluation of the hand with plain view x-rays are helpful and may reveal bone involvement (FIG 5).

For both SCC and melanoma, a chest radiograph, complete blood count, and liver panel may be obtained. If these labs reveal abnormality, prompt evaluation by an internist or oncologist is appropriate.

More detailed imaging studies (computed tomography [CT], magnetic resonance imaging [MRI], and positron emission tomography [PET]) may be performed to evaluate specific organ systems (central nervous system, pulmonary, gastrointestinal, and others) if indicated.

The diagnosis of skin cancer requires adequate histopathologic evaluation with a full-thickness (surface to full depth) specimen.

SCC is graded 1 to 4 based on the proportion of differentiating cells present and the frequency of atypical tumor cells.

Melanoma subtypes include the following:

Malignant melanoma staging is determined by histopathologic evaluation of the vertical thickness of the lesion in millimeters (Breslow classification) or the anatomic level of local invasion (Clark classification).

Along with the presence of ulceration, Breslow thickness more accurately predicts melanoma behavior in lesions thicker than 1.5 mm. Estimates of prognosis should be modified by sex and anatomic site in coordination with clinical and histologic evaluation.

The Clark classification ranges from level I (in situ lesions involving only the epidermis) to level V (invasion through the reticular dermis into the subcutaneous tissue).