BASAL CELL CARCINOMA

Basal cell carcinoma (BCC) is a malignant neoplasm originating from the basal cells of the epidermis. It accounts for ~80% of all skin cancers, making it the most common type of skin cancer, as well as the most common cancer overall. BCCs are usually slow-growing tumors that arise without a precursor lesion and may be locally aggressive or recurrent, but rarely metastasize. These lesions typically occur due to ultraviolet (UV) exposure and are seen most frequently on sun-exposed areas—particularly the head and neck—while only ~10% of cases develop on the hand and upper extremity. Individuals with fair skin and a history of intermittent, extreme sun exposure have an elevated risk for BCCs, and the majority of cases are seen in patients over the age of 40. However, a number of rare genetic disorders may predispose some individuals and their families to the development of numerous BCCs. ^1-4

Pathophysiology

• The primary risk factor for BCC is excessive exposure to UV radiation (UVR), particularly UV-B. The mechanisms that lead to tumor formation after UVR exposure include direct DNA damage, indirect DNA damage through reactive oxygen species, and local cutaneous immune suppression.^3,5
• Other risk factors for BCCs include blistering sunburns sustained during childhood, family history of skin cancer, tanning bed use (a risk factor associated with BCC development in younger patients), chronic immunosuppression, photosensitizing drugs, exposure to ionizing radiation, and exposure to carcinogenic chemicals, (arsenic predisposes patients to SCCs, less frequently BCCs).⁶
• Literature suggests that BCCs arise from immature, pluripotent cells associated with the hair follicle.³

Related Anatomy

• Dermis
• Epidermis
• Basal cells
• Basaloid cells
• Pluripotent cells
• Hair follicles
• The four major subtypes of BCC are: 
  • Nodular (50-65% of cases)
  • Superficial (15-20%)
  • Pigmented (5%) 
  • Infiltrative; Sclerosing or morpheaform (1-3%)^3,4

Incidence and Related Conditions

• The incidence of BCC jumped from 20% to 80% over the last 30 years and is increasing annually by ~4-8%. BCCs currently affects ~2.8 million people each year.^3,5,6
• BCCs are most common in Fitzpatrick skin types I and II, and these populations have an estimated lifetime risk of 30%.⁶
• The incidence rate for BCC increases with age, with most cases occurring over the age of 40 years and the median age for diagnosis being 68 years.^2,3
• BCCs most commonly occur on the head and trunk (>75% of cases), while only ~10%  occur on hands and upper extremities.²
• Albinism
• Basex-Dupré-Christol syndrome
• Darier’s disease
• Gorlin syndrome (basal cell nevus syndrome)
• Melanoma
• Squamous cell carcinoma
• Xeroderma pigmentosa

Differential Diagnosis

• Actinic keratosis
• Bowen’s disease
• Dermatitis
• Malignant melanoma (especially amelanotic melanoma)
• Melanocytic nevi
• Merkel cell carcinoma
• Molluscum contagiosum
• Psoriasis
• Sebaceous hyperplasia
• Seborrheic keratosis
• Squamous cell carcinoma
• Trichoblastoma
• Trichoepithelioma

A typical patient is a 65-year-old man with Fitzpatrick skin type II, blue eyes, and blonde hair. The man was born and raised in Tucson, AZ, and spent the majority of his working days outdoors as a contractor, often without wearing any sunscreen. He was recently washing his hands when he observed the formation of a papule on the dorsum of his left wrist. After several weeks, the pink lesion began to take on the appearance of a dome shape with clearly defined borders, and was mildly tender to the touch due to ulceration. Concerned with the possibility of the lesion being cancerous, he consulted with his dermatologist for a skin examination.

• Infection
• Scarring
• Erythema
• Swelling
• Erosions

• Death rates are generally very low in BCC, (unlike SCC, immunosuppression does not appear to increase risk of BCC metastasis). The prognosis for BCC is mainly related to its potential risk of recurrence after initial therapy, which depends on the lesion’s location and clinical and histopathological features.³
• Metastases rates for BCC are extremely low, occurring in less than 0.003-0.6% of all cases. 
• Mohs micrographic surgery has been associated with the best long-term cure rate of any treatment for BCC. This technique also minimizes the wound size and often leads to a superior cosmetic outcome as well.³
  • The 5-year recurrence rate after surgical excision is 3-10% for primary tumors and >17% for recurrent BCCs, but after Mohs surgery, it’s 1.0-1.7% for primary tumors and 4.0-5.6% in recurrent cases.²

• After treatment, patients should be monitored closely in the long term—possibly for life—particularly those with multiple or high-risk tumors.³
• All patients with BCC should be referred to dermatology for routine skin examinations.
• Although BCCs have low mortality rates, they can cause significant morbidity, primarily through local destruction.⁶
• The low occurrence of BCCs on the hands and upper extremities is odd, as other types of skin cancers like squamous cell carcinoma occur just as frequently in these areas as they do on other sun-exposed parts of the body.⁵ 
• The risk of metastasis from basal cell skin cancers is low, but increases with size and is most closely associated with tumors >3 cm.^1-3
• Shave, punch, or excision biopsy is recommended for suspected BCCs to confirm the diagnosis.^2,3  The characteristic feature of BCCs is islands or nests of basaloid cells, with cells palisading at the periphery in a haphazard arrangement in the centers of the islands.³
• The hallmark of BCCs under dermatoscope is the presence of well-focused arborizing vessels that cross the midline of the lesion. Additional findings include multiple blue-gray globules, leaf-like structures, large blue-gray ovoid nests, and spoke-wheel areas.³

Cited

1. Marks JG, Miller JJ. Lookingbill and Marks’ Principles of Dermatology. Fifth Ed. London, New York: Saunders Elsevier; 2013.
2. Ilyas EN, Leinberry CF, Ilyas AM. Skin cancers of the hand and upper extremity. J Hand Surg Am 2012;37(1):171-178.PMID: 22196297
3. McDaniel B, Badri T. Basal Cell Carcinoma. In: StatPearls.Treasure Island (FL) 2019.PMID: 29494046
4. English C, Hammert WC. Cutaneous malignancies of the upper extremity. J Hand Surg Am 2012;37(2):367-377. PMID: 22281171
5. Loh TY, Rubin AG, Brian Jiang SI. Basal Cell Carcinoma of the Dorsal Hand: An Update and Comprehensive Review of the Literature. Dermatol Surg 2016;42(4):464-470.PMID: 27002472
6. Kim DP, Kus KJB, Ruiz E. Basal Cell Carcinoma Review. Hematol Oncol Clin North Am 2019;33(1):13-24.PMID: 30497670
7. Tanese K. Diagnosis and Management of Basal Cell Carcinoma. Curr Treat Options Oncol 2019;20(2):13.PMID: 30741348
8. James WD, Berger TG, Elston DM. Andrews’ Diseases of the Skin.12^thEd. Philadelphia, PA. Elsevier, 2016.

New articles

1. Neal DE, Feit EM, Etzkorn JR. Patient Preferences for the Treatment of Basal Cell Carcinoma: A Mapping Review of Discrete Choice Experiments. Dermatol Surg2018;44(8):1041-1049. PMID: 30045140
2. Cameron MC, Lee E, Hibler BP, et al. Basal cell carcinoma: Epidemiology; pathophysiology; clinical and histological subtypes; and disease associations. J Am Acad Dermatol2019;80(2):303-317. PMID: 29782900

Reviews

1. Loh TY, Rubin AG, Brian Jiang SI. Basal Cell Carcinoma of the Dorsal Hand: An Update and Comprehensive Review of the Literature. Dermatol Surg 2016;42(4):464-470.PMID: 27002472
2. Kim DP, Kus KJB, Ruiz E. Basal Cell Carcinoma Review. Hematol Oncol Clin North Am 2019;33(1):13-24.PMID: 30497670