Basal cell carcinoma

From Wikipedia, the free encyclopedia

Basal cell carcinoma Classification and external resources
ICD-9	173
ICD-O:	8090/3-8093/3
OMIM	605462
DiseasesDB	1264
eMedicine	med/214
MeSH	D002280

Basal cell carcinoma (BCC) is the most common form of skin cancer.^[1] It can be destructive and disfiguring. The risk of developing BCC is increased for individuals with a family history of the disease and with a high cumulative exposure to UV light via sunlight^[1].Treatment is with surgery, mohs surgery, topical chemotherapy, X-ray, cryosurgery, or photodynamic therapy. It is rarely life-threatening but, if left untreated, can be disfiguring, cause bleeding, and produce local destruction (e.g., eye, ear, nose, lip). As with squamous cell carcinoma, the incidence of basal cell carcinoma rises sharply with immunosuppression and in patients with inherited defects in DNA repair.^[2]Basal cell skin cancer almost never spreads; however, large and longstanding tumours may metastasize into regional lymph nodes and surrounding areas such as nearby tissues and bone.^[1]

Contents 1 Forms 2 Presentation 3 Diagnosis 4 Pathophysiology 5 Prevention and early diagnosis 6 Treatment 7 Prognosis 8 Epidemiology 9 Notes 10 References 11 External links

Forms

Various forms are recognized:

• Nodular: flesh-colored papule with telangiectasis; if it ulcerates, it becomes a "rodent ulcer" (ulcus rodens), an ulcerating nodule with (often) a pearly border
• Cystic: rarer and difficult to distinguish from the nodular form, which has a central cavity with fluid
• Pigmented: a variant of the nodular form that may be confused with melanoma
• Sclerosing/cicratising: a scar-like lesion
• Superficial: a red scaling patch.

About two-thirds of basal cell carcinomas occur on sun-exposed areas of the body. One-third occur on areas of the body that are not exposed to sunlight, emphasizing the genetic susceptibility of the basal cell cancer patients.

Basal cell carcinoma

Presentation

Basal cell carcinomas present as a firm nodule, clearly growing within the skin and below it, rather than on the surface.

Color varies from that of normal skin to dark brown or black, but there is a characteristic "pearly white" translucent quality on the periphery.

Basal cell carcinomas display a characteristic "rolled edge." Once the basal cells have invaded the deeper tissues, the rolled edge disappears.

When BCCs occur at sites other than the face and neck, they are usually just red, flat, scaling areas. Thus, superficial BCCs can often be confused with a patch of eczema.

Diagnosis

To diagnose basal cell carcinomas, a biopsy (where tissue is taken for pathological study) is done using local anesthesia. In small lesions, the tumor is, in general, removed in its entirety, whereas larger ones are biopsied first and surgically removed later if it is confirmed that it is malignant.

Histopathology: Basal cell carcinoma is a malignant epithelial tumor arising only in skin, from the basal layer of the epidermis or of the pilosebaceous adnexa. Tumor is represented by compact areas, well delineated and invading the dermis, apparent with no connection with the epidermis. Tumor cells resemble normal basal cells (small, monomorphous) and are disposed in palisade at the periphery of the tumor nests, but are spindle-shaped and irregular in the middle. Tumor clusters are separated by a reduced stroma with inflammatory infiltrate. 1

Pathophysiology

Basal cell carcinomas develop in the basal cell layer of the skin. Sun light exposure leads to the formation of thymine dimers, a form of DNA damage. While DNA repair removes most UV-induced damage, not all crosslinks are excised. There is, therefore, cumulative DNA damage leading to mutations. Apart from the mutagenesis, sunlight depresses the local immune system, possibly decreasing immune surveillance for new tumor cells.

Basal-cell carcinoma also develops as a result of basal-cell nevus syndrome, or Gorlin's syndrome, which is also characterized by odontogenic keratocysts of the jaw, palmar or plantar (sole of the foot) pits, calcification of the falx cerebri (in the center line of the brain) and rib abnormalities. The cause of the syndrome is a mutation in the PTCH1 tumor-suppressor gene at chromosome 9q22.3, which inhibits the hedgehog signaling pathway. A mutation in the SMO gene, which is also on the hedgehog pathway, also causes basal-cell carcinoma.^[3]

Prevention and early diagnosis

Basal cell carcinoma is the most common skin cancer. It occurs mainly in fair-skinned patients with a family history of this cancer. Sunlight is a factor in about two-thirds of these cancers, but one-third occur in non-sun-exposed areas. Therefore, doctors recommend sun screens.

Treatment

The following methods are employed in the treatment of basal cell carcinoma (BCC):

• Surgery: Most basal cell carcinomas are removed by surgery. A common method is electrodessication and curettage (ED&C). This is done by scraping the tumor out with a curette and cauterizing the base and margins. The wound is left to heal by itself (secondary intention healing). While it is considered cost-effective, recurrences [1] and the requirement for more extensive surgery make this procedure unacceptable for younger patients as well as cancers of the face, hands, or fingers. The cure rate can be very poor, as the margins are undefined and no histological proof of "cure" is allowed. The dermis is often thinned with this procedure, causing bulging of tissue, and unsightly white scalloped scar. Surgical excision is another option with the margins of excised tissue examined under the microscope. Cure rate can be excellent with wide excisional margins (4-6mm), or very poor with narrow surgical margins (1-2mm). Certain types, like the sclerosing basal cell cancers, may need a wider margin, as they develop subtle processes that project outside the visible part of the tumor. Although BCCs are carcinomas, they very rarely metastasize^[4]. They are invasive cancers; they can cause significant local tissue loss and even death. Despite this, basal cell carcinomas are not formally included in national cancer statistics, probably due to the extreme rarity of metastasis.

• Chemotherapy: Some superficial cancers respond to local therapy with 5-fluorouracil, a chemotherapy agent. Topical treatment with 5% Imiquimod cream, with five applications per week for six weeks has a reported 70-90% success rate at reducing, even removing, the BCC [basal cell carcinoma]. Imiquimod may be used prior to surgery in order to reduce the size of the carcinoma. One can expect a great deal of inflammation with this treatment^[5].

• Radiation: Radiation therapy is still appropriate in older patients that are not candidates for surgery.

• Cryosurgery: Cryosurgery is another option, particularly for basal cell cancer that invades cartilage, as the healthy cartilage is cryo-resistant.

• Mohs surgery: Mohs surgery (or Mohns micrographic surgery) is an outpatient procedure in which the tumor is surgically excised and then immediately examined under a microscope. The base and edges are microscopically examined to verify sufficient margins before the surgical repair of the site. If the margins are insufficient, more is removed from the patient until the margins are sufficient. It is also used for squamous cell carcinoma; however, the cure rate is not as high as Mohs surgery for basal cell carcinoma.

• Immunotherapy: Immunotherapy research suggests that treatment using Euphorbia peplus, a common garden weed, may be effective^[6]. Australian biopharmaceutical company Peplin^[7] is developing this as topical treatment for BCC.

Treating surgeons will recommend one of these modalities as appropriate treatment depending on the tumor size, location, patient age, and other variables.

Prognosis

Although basal cell carcinoma rarely metastasizes, it grows locally with invasion and destruction of local tissues, without stopping. The cancer can impinge on vital structures and result in loss extension or loss of function or rarely death. The vast majority of cases can be successfully treated before serious complications occur.

Epidemiology

Basal cell cancer is the most common skin cancer. It is much more common in fair-skinned individuals with a family history of basal cell cancer and increases in incidence closer to the equator or at higher altitude. According to Skin Cancer Foundation[2], there are approximately 800,000[3] new cases yearly in the United States alone.

Most sporadic BCC arises in small numbers on sun-exposed skin of people over age 50, although younger people may also be affected. The development of multiple basal cell cancer at an early age could be indicative of Nevoid basal cell carcinoma syndrome.

Notes

1. ^ ^{a b c} "MedlinePlus Medical Encyclopedia: Basal cell carcinoma" (symptoms/treatment), U.S. National Library of Medicine, 8600 Rockville Pike, Bethesda, MD, and National Institutes of Health, USA, October 2007, webpage: BCC.
2. ^ Kumar, Abbas, Fausto. Robbins and Cotran Pathological Basis of Disease 7E.  : , 1999. p. 1241-1243
3. ^ Epstein EH et al., Case 3-2008: An 80-year-old woman with cutaneous basal-cell carcinoma and cysts of the jaw, N Engl J Med (2008) 358:393-401
4. ^ Uzquiano MC, Prieto VG, Nash JW, Ivan DS, Gong Y, Lazar AJ, Diwan AH.Metastatic basal cell carcinoma exhibits reduced actin expression. Mod Pathol. 2008 Jan 25 <http://www.ncbi.nlm.nih.gov/pubmed/18223552?ordinalpos=5&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum>
5. ^ The Skin Cancer Foundation - The Skin Cancer Foundation Seal of Recommendation
6. ^ Peplin's skin cancer gel trial a success - Breaking News - Business - Breaking News
7. ^ Peplin

References

[4]http://www.cancer.org/docroot/CRI/content/CRI_2_4_4X_Treatment_of_Basal_Cell_Carcinoma_51.asp

• "MedlinePlus Medical Encyclopedia: Basal cell carcinoma" (symptoms/treatment), MedlinePlus Medical Encyclopedia, U.S. National Library of Medicine, 8600 Rockville Pike, Bethesda, MD, and National Institutes of Health, USA, October 2007, webpage: BCC.

[5] Surgical excision vs Mohs' micrographic surgery for basal-cell carcinoma of the face: randomised controlled trial.

External links

• [6]http://www.cancer.org/docroot/CRI/content/CRI_2_4_4X_Treatment_of_Basal_Cell_Carcinoma_51.asp
• The Skin Cancer Foundation
• Natural history of Basal cell carcinoma
• Basal cell carcinoma of the nose

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