The most common nodular type is a smooth, skin-colored, indurated, dome-shaped papule with a rolled edge. Other attributes include a pearly appearance, overlying telangiectatic vessels, and a history of bleeding with minor trauma.7,11
Superficial basal cell carcinoma is similar to dermatitis but more often has distinct borders and a bright pink appearance.11 If in doubt about the diagnosis, obtain a tissue sample for pathology.
Squamous cell carcinoma
Squamous cell carcinoma most often is a small, firm, hyperkaratotic nodule sitting atop an inflamed base. It may also be skin-colored and smooth. The history can include itching, pain, and nonhealing after minor trauma.7,11,12 As with basal cell carcinoma, diagnosis is made by tissue pathology.
Malignant melanoma
Malignant melanoma usually appears as a changing or unusual mole with haphazard color variegation, including combinations of brown, black, blue, gray, white, and (rarely) pink. Most melanomas are larger than 5 mm in diameter at time of diagnosis.13
There are 4 main types of malignant melanoma:
- Superficial spreading melanoma accounts for 50% of cases and occurs more frequently in younger adults.
- Nodular melanoma also occurs in younger adults, representing 20% to 25% of cases.
- Lentigo maligna melanoma occurs in older adults and accounts for only 15% of cases.
- Acral or acral-lentiginous melanomas are the least common form (10% of cases). They appear on the palms, soles, and around the first toenail.14
Risk factors for skin malignancies
Factors conferring the highest relative risk for malignant melanoma include:13
- atypical nevus syndrome with a personal and family history of melanoma
- history of a changing mole
- atypical nevus syndrome with just a family history of melanoma
- age greater than or equal to 15 years
- history of dysplastic moles.
Table 1 provides a list of risk factors that should prompt an annual skin survey (LOE: 5).
For nonmelanoma skin cancers, the strongest risk factors ( Table 2) include Caucasian race; age 55 to 75 years; and male sex.2 There is good evidence that a history of nonmelanoma skin cancer confers a 10-fold risk for recurrence (LOE: 2a).15 A distinct risk factor for squamous cell carcinoma is immunosuppression.2 Table 2 also provides a complete list of risk factors for nonmelanoma skin cancer.
Precursor lesions for nonmelanoma skin cancers include Bowen’s disease and erythroplasia of Queyrat (forms of squamous cell carcinoma in situ that will progress if left untreated). Actinic keratoses are common precursor lesions, but their overall annual rate of malignant transformation is only 1 in 400. In the case of SCC, up to 60% of cancers develop from an existing actinic keratosis.2
TABLE 1
Risk factors for malignant melanoma 13
| Risk factors that should prompt an annual skin survey | RR (LOE)* |
|---|---|
| Atypical nevus syndrome with personal and family history of melanoma | 500 (1b) |
| Changing mole | >400 (4) |
| Atypical nevus syndrome with family history of melanoma | 148 (1b)† |
| Age ≥ 15 | 88 (2c) |
| Dysplastic moles | 7–70 (3b) |
| History of melanoma before age 40 | 23 (2b) |
| Large congenital nevus (≥15 cm) | 17 (2b) |
| Caucasian race | 12 (2b) |
| Lentigo maligna | 10 (2c) |
| Atypical nevi | 7–27 (3b) |
| Regular use of tanning bed before age 30 | 7.7‡ (3b) |
| Multiple nevi | 5–12 (3b) |
| Personal history of melanoma | 5–9 (2b) |
| Immunosupression | 4–8 (2b) |
| Family history (first degree) of melanoma | 3–8 (3b) |
| Nonmelanoma skin cancer | 3–5 (3b) |
| Sun sensitivity or tendency to burn | 2–3 (3b) |
| *See page 239 for a description of levels of evidence | |
| †(95% CI, 40–379) | |
| ‡(95% CI, 1–63.6) | |
| RR, relative risk (compared with person without risk factors); | |
| LOE, level of evidence; | |
| CI, confidence interval | |
TABLE 2
Risk factors for nonmelanoma skin cancer
| Significant risk factors | RR | LOE* |
|---|---|---|
| Caucasian race | 70 | 2c |
| Immunosuppression | 5–20 | 2c |
| Previous nonmelanoma skin cancer | 10 | 2a |
| Age 55–75 | 4–8 | 2c |
| Male sex | 2 | 2c |
| Genetic risk factors associated with nonmelonoma skin cancer 3 | ||
| ||
| Chemical exposure risk factors associated with nonmelonoma skin cancer (particularly squamous cell carcinoma) 3 | ||
| ||
| Environmental factors and medical conditions associated with nonmelonoma skin cancer (particularly squamous cell carcinoma) 3 | ||
| ||
| *See page 239 for a description of levels of evidence | ||
| RR, relative risk (compared with person without risk factors); LOE, level of evidence | ||
Clinical prediction rules for skin malignancies
Malignant melanoma
ABCDE criteria. A useful clinical prediction rule for malignant melanoma is the American Cancer Society’s “ABCDE criteria” (Table 3). This rule was validated in 4 dermatology clinics, studying a total of 1118 lesions, although the studies were not homogenous (strength of recommendation [SOR]: A).16-19 Results of the study are summarized in Table 4. The test is normally considered positive if one or more of the criteria are met; however, as more criteria are met, specificity increases while sensitivity decreases.17-19
For lesions lacking any of the ABCDE criteria, 99.8% are something other than melanoma (using a prevalence of 1% found in the US population) (SOR: A). Use caution, however, as this rule will miss amelanotic melanomas, as well as smaller melanomas that are changing in size or have other features suggestive of malignant melanoma.