Basal cell carcinoma (BCC), the most common form of skin cancer in Caucasians, will affect about two million Americans this year. According to one estimate, a 16-year-old Caucasian living in the US today has a 28 to 33 percent lifetime risk for developing BCC.¹ Although with less frequency, BCC occurs in African-American and other dark-skinned individuals. BCC is associated with excessive UV-exposure and occurs most frequently on sun-exposed body sites, such as the face and arms, however, it can occur anywhere on the body, including areas rarely exposed to light, such as the axilla, buttocks, inguinal crease (Fig. 1), and thighs. Clinicians must be prepared to recognize unusual variants and able to identify BCCs that occur in unusual anatomic locations.

BCC Overview
The most common forms of BCC are superficial and nodular. According to one analysis, nodular BCCs are most common, accounting for 57.6 percent of all BCCs in a clinical cohort of 1,711 subjects with 2,990 histologically confirmed BCCs.² Superficial BCCs accounted for 16.2 percent of all BCCs in the same cohort. Nodular BCCs were found to occur more frequently in males and in older patients (those age 60 to 79 had the younger patients. The mean age at diagnosis of superficial BCC was 57.5 years, compared to 65.5 years for nodular BCC.

Compared to individuals over age 90, those patients aged 40 and younger who were diagnosed with BCC had a higher prevalence of the cancers on the trunk (59.3 percent versus 31.5 percent).³ Older patients had a higher prevalence of BCCs on the head and neck (57.3 percent versus 36.0 percent) and of superficial BCCs (43 percent versus 31.5 percent). Superficial BCCs were mostly on the trunk, morpheic BCCs were mostly on the head and neck, and nodular BCCs were mostly on the head and neck, in this cohort.

A recent analysis suggests that the incidence of BCC in women may be on the rise.4 Overall, the ageadjusted incidence of basal cell carcinoma per 100,000 persons was 25.9 for women and 20.9 for men, and the incidence of BCC increased significantly during the study period among women only. Among all patients, nodular BCC was the most common histologic subtype (43 percent), while an additional 11 percent of patients had a mixed composition that included the nodular subtype.

BCC Clinical Subtypes and Characteristics Nodular or Nodulo-ulcerative BCC

• Skin-colored, pink, gelatinous, translucent, pearly, grey nodules form.
• A central depression is commonly seen, and telangiectatic vessels may be noted.
• Gradual enlargement leads to central ulceration and peripheral, “rolled” border.
• Erosion with crust may be seen.
• As noted, this is the most common clinical presentation.

Cystic BCC

• A fluid-filled, smooth, round, pink-red, telangiectatic nodule/mass is noted.
• Incision and drainage will exude a clear mucinous fluid.

Morpheaform/Sclerosing BCC

• Classic presentation is a whitish, waxy, sclerotic plaque with ill-defined borders that resembles localized scleroderma.
• Most commonly affected sites are the nasolabial fold or forehead.
• Lesions may be depressed and firm, resembling a scar.
• This is the least common but most aggressive form of BCC.

Superficial Spreading Multicentric BCC

• Erythematous, scaly, plaques with slightly elevated “rolled” edges are extrafacial, occurring on the limbs or trunk.
• Lesions demonstrate slow centrifugal growth.
• Erosions, crusts, and nodules are commonly seen.
• This is the least aggressive BCC subtype.

Pigmented BCC

• Marked by a brownish to blue-black pigmentationand a pearly surface, this subtype is seen in moredarkly pigmented individuals.
• Due to this phenotypic distribution, as a generalrule of thumb, pigmented BCC is more likely in individualswith brown eyes, whereas similar appearinglesions in those with blue or green eyes are morelikely to be melanoma.

Fibroepithelioma of Pinkus BCC

• Extremely rare, with a predisposition to women,this form of BCC usually appears on the lower anteriorabdominal wall.
• Sessile, firm, flesh-to-pink-to-red or reddish-browncolored nodules or plaques on the abdomen or thighare commonly seen.
• The appearance of these lesions can be similar tothat of seborrheic keratosis.

Depressed BCC

• As its name suggests, this form of BCC appears likea depressed scar, however, an important clinical clueis an absence of history of local trauma.
• Lesions often have a sharp drop-off and craterformedges.
• Males are more frequently affected, with the centralthird of the face being the most common site ofinvolvement.

• Flesh-to-pink colored papules with telangiectasescan mimic a nevus.
• The most common site of occurrence is the centralthird of the face.
• This form of BCC may develop as early as 12 yearsof age.

Recurrent BCC
Recurrence rates for BCC range as high as 32 percent.⁵ Incomplete excision or destruction are oftencited as primary reasons for recurrence, althoughthese do not appear to account for all recurrences.There are six primary features that may characterizerecurrent BCCs:
1. Superficial in the scar tissue
2. On the border of the scar tissue (Fig. 2)
3. Deep in the dermis or subcutaneous tissue
4. Deep recurrences show a normal or brownish erythematoussurface
5. Erosions in or on the border of the scar
6. Mimic epidermal cysts.

Index of Suspicion
The clinical diagnosis of basal cell carcinoma presentschallenges. Multiple subtypes exist, each withvarying presentations. Furthermore, while tumorsmost frequently occur on body sites commonlyexposed to UV radiation, such as the face, chest, and arms, tumors may develop on virtually anybody site. Unusual sites of involvement may complicatethe diagnosis.

While tools such as dermatoscopes improve theclinician's ability to confidently diagnose skin cancers(melanoma), and modalities such as Mohsmicrographic surgery offer improved therapeuticoutcomes, the initial identification of suspicioustumors depends on keen-eyed clinicians. The developmentof a visual memory store of unusual lesiontypes and locations is an essential tool for the dermatologist.To see more examples of BCCs on unusualbody sites, log onto PracticalDermatology.com orDermEdOnline.com.

Dr. Bikowki has no relevant disclosures.

1. Lear JT, Smith AG. Basal cell carcinoma. Postgrad Med J. 1997 Sep;73(863):538-42.
2. Bastiaens MT, Hoefnagel JJ, Bruijn JA, Westendorp RG, Vermeer BJ, Bouwes Bavinck JN.Differences in age, site distribution, and sex between nodular and superficial basal cell carcinomaindicate different types of tumors. J Invest Dermatol. 1998 Jun;110(6):880-4.
3. Betti R, Radaelli G, Mussino F, Menni S, Crosti C. Anatomic location and histopathologicsubtype of basal cell carcinomas in adults younger than 40 or 90 and older: any difference?Dermatol Surg. 2009 Feb;35(2):201-6.
4. Christenson LJ, Borrowman TA, Vachon CM, Tollefson MM, Otley CC, Weaver AL, Roenigk RK.Incidence of basal cell and squamous cell carcinomas in a population younger than 40 years.JAMA. 2005 Aug 10;294(6):681-90.
5. Santiago F, Serra D, Vieira R, Figueiredo A. Incidence and factors associated with recurrenceafter incomplete excision of basal cell carcinomas: a study of 90 cases. J Eur AcadDermatol Venereol. 2010 Apr 8. Epub

Take-Home Tips.
Basal cell carcinoma (BCC), is the mostcommon form of skin cancer in Caucasians. It occurs with lessfrequency in African-American and other dark-skinnedindividuals. BCC is associated with excessive UV-exposure and occursmost frequently on sun-exposed body sites, such as the face andarms, however, it can occur anywhere on the body, including areasrarely exposed to light, such as the axilla, buttocks, inguinal crease,and thighs. The most common forms of BCC are superficial andnodular. Clinicians must be prepared to recognize unusual variantsand able to identify BCCs that occur in unusual anatomic locations.

Visual Cues.
This article is the first in an occasionalseries that will support the development of a clinician's visual memory store. Additional resourcesare posted at PracticalDermatology.com andDermEdOnline.com.

ALL IMAGES BELOW COURTESY OF JOSEPH BIKOWSKI, MD AND DermEdOnline.com