Animal-type melanoma

Animal-type melanoma can develop anywhere on the body, similar to general malignant melanoma.{{cite book |last1=Schwartzman |first1=Robert Mayer |title=A Comparative Study of Diseases of Dog and Man |last2=Orkin |first2=Milton |date=1962 |publisher=Thomas |location=Springfield, IL |page=85 |quote=The term 'melanoma' in human medicine indicates a malignant growth; the prefix 'malignant' is redundant.}} It will be observed as arising from normal, unaffected skin, rather than skin with a pre-existing mole. Animal-type melanoma appears as a dark brown/black papule and resembles a melanocytic tumor in grey horses.

Early signs of animal-type melanoma can be summarized by the ABCDE criteria, excluding the E.

• Asymmetry
• Border irregularity
• Color variation
• Diameter more than 6mm

Animal-type melanoma has the same likelihood of causes as general malignant melanoma. Fair skin, family history, and sun damage are all common and well-known risk factors. Melanomas are usually caused by DNA damage resulting from exposure to UV light from the sun. Genetics also play a role{{cite news |title=Melanoma Risk factors |work=Mayo Clinic |url=http://www.mayoclinic.org/diseases-conditions/melanoma/basics/risk-factors/con-20026009 |url-status=live |access-date=10 April 2017 |archive-url=https://web.archive.org/web/20170410133759/http://www.mayoclinic.org/diseases-conditions/melanoma/basics/risk-factors/con-20026009 |archive-date=10 April 2017}}{{cite journal |vauthors=Greene MH |date=December 1999 |title=The genetics of hereditary melanoma and nevi. 1998 update |journal=Cancer |volume=86 |issue=11 Suppl |pages=2464–77 |doi=10.1002/(SICI)1097-0142(19991201)86:11+<2464::AID-CNCR3>3.0.CO;2-F |pmid=10630172 |s2cid=32817426|doi-access=free }} and is responsible for melanoma occurring in skin areas with little sun exposure (i.e. mouth, feet soles, palms, and genital areas).{{cite book |vauthors=Goydos JS, Shoen SL |chapter=Acral Lentiginous Melanoma |series=Cancer Treatment and Research |date=2016 |title=Melanoma |volume=167 |pages=321–9 |doi=10.1007/978-3-319-22539-5_14 |isbn=978-3-319-22538-8 |pmid=26601870}}

A weakened immune system aids in cancer development due to a lack of ability to fight cancer cells. Having more than 50 moles is also an indication of an increased risk of melanoma.{{cite news |title=Melanoma Risk factors |work=Mayo Clinic |url=http://www.mayoclinic.org/diseases-conditions/melanoma/basics/risk-factors/con-20026009 |url-status=live |access-date=10 April 2017 |archive-url=https://web.archive.org/web/20170410133759/http://www.mayoclinic.org/diseases-conditions/melanoma/basics/risk-factors/con-20026009 |archive-date=10 April 2017}}

UVA and UVB rays are wavelengths expressed by the sun and absorbed by skin cell DNA that results in DNA damage.{{cite journal |vauthors=Rünger TM, Farahvash B, Hatvani Z, Rees A |date=January 2012 |title=Comparison of DNA damage responses following equimutagenic doses of UVA and UVB: a less effective cell cycle arrest with UVA may render UVA-induced pyrimidine dimers more mutagenic than UVB-induced ones |journal=Photochemical & Photobiological Sciences |volume=11 |issue=1 |pages=207–15 |doi=10.1039/c1pp05232b |pmid=22005748 |s2cid=25209863|doi-access=free }} Exposure to radiation (UVA and UVB) is one of the major contributors to the development of melanoma.{{cite journal |vauthors=Wang SQ, Setlow R, Berwick M, Polsky D, Marghoob AA, Kopf AW, Bart RS |date=May 2001 |title=Ultraviolet A and melanoma: a review |journal=Journal of the American Academy of Dermatology |volume=44 |issue=5 |pages=837–46 |doi=10.1067/mjd.2001.114594 |pmid=11312434 |s2cid=7655216}} Likewise, occasional extreme sun exposure (sunburn) is related to melanoma.{{cite journal |vauthors=Oliveria SA, Saraiya M, Geller AC, Heneghan MK, Jorgensen C |date=February 2006 |title=Sun exposure and risk of melanoma |journal=Archives of Disease in Childhood |volume=91 |issue=2 |pages=131–8 |doi=10.1136/adc.2005.086918 |pmc=2082713 |pmid=16326797}} The use of sunbeds that contain deeply penetrating UVA rays has also been linked to the development of melanoma.{{Cite web |title=WHO | The World Health Organization recommends that no person under 18 should use a sunbed |url=https://www.who.int/mediacentre/news/notes/2005/np07/en/ |url-status=dead |archive-url=https://web.archive.org/web/20090616124844/http://www.who.int/mediacentre/news/notes/2005/np07/en/ |archive-date=16 June 2009 |website=WHO}}

Having multiple severe sunburns increases the likelihood that future sunburns develop into melanoma. This is due to cumulative damage.{{cite news |title=Melanoma Risk factors |work=Mayo Clinic |url=http://www.mayoclinic.org/diseases-conditions/melanoma/basics/risk-factors/con-20026009 |url-status=live |access-date=10 April 2017 |archive-url=https://web.archive.org/web/20170410133759/http://www.mayoclinic.org/diseases-conditions/melanoma/basics/risk-factors/con-20026009 |archive-date=10 April 2017}}

When determining risk for melanoma, the intensity and duration of sun exposure, the age at which sun exposure occurs, and the degree of skin pigmentation all play a role.{{cite journal |vauthors=Khlat M, Vail A, Parkin M, Green A |date=May 1992 |title=Mortality from melanoma in migrants to Australia: variation by age at arrival and duration of stay |journal=American Journal of Epidemiology |volume=135 |issue=10 |pages=1103–13 |doi=10.1093/oxfordjournals.aje.a116210 |pmid=1632422}} Familial melanoma is known as melanoma passed from generation to generation within a family. Two genes, CDKN2A and CDK4, have been linked to familial melanoma. When a mutation occurs in either of these genes, it will result in an increased risk of melanoma. While these two are primarily linked, the alterations in these genes only account for a small percentage of familial melanoma.{{Cite web |date=2012-06-25 |title=Familial Malignant Melanoma |url=https://www.cancer.net/cancer-types/familial-malignant-melanoma |access-date=2023-03-19 |website=Cancer.Net |language=en}}

Familial melanoma follows an autosomal dominance inheritance pattern where a mutation happens in only one copy of the gene. This means a parent gene may either pass along a copy of their normal gene or a copy of the gene with the mutation.

By the time animal-type melanoma has been diagnosed, it likely has been a year or longer since it was first present on the skin. After a clinical assessment acknowledges a lesion on the skin that may point to melanoma, a dermascopic analysis may be required.{{Cite journal |last1=Li |first1=Suli |last2=Chu |first2=Yihang |last3=Wang |first3=Ying |last4=Wang |first4=Yantong |last5=Hu |first5=Shipeng |last6=Wu |first6=Xiangye |last7=Qi |first7=Xinwei |date=2022-10-14 |title=Distinguish the Value of the Benign Nevus and Melanomas Using Machine Learning: A Meta-Analysis and Systematic Review |journal=Mediators of Inflammation |volume=2022 |pages=1–8 |doi=10.1155/2022/1734327|pmid=36274972 |pmc=9586788 |doi-access=free }} When under analysis, animal-type melanoma appears to have a structureless blue pattern, irregular whitish structures, and irregular, large blood vessels.

If determined to be melanoma, the lesion may be removed with an excision biopsy (completely cutting out and removing a skin lesion).{{Cite web |title=Excision of skin lesions {{!}} DermNet |url=https://dermnetnz.org/topics/excision-of-skin-lesions |access-date=2023-03-19 |website=dermnetnz.org}} A histology report that determines animal-type melanoma may include:

• Heavily pigmented melanocytic tumor
• Epithelioid and splindled melanocytes
• Bland or malignant cytological appearance
• Low mitotic activity
• Infrequent ulceration
• No features to suggest regression

Due to the unknown nature of animal-type melanoma, a pathologist may find it challenging to make a definite diagnose between animal-type melanoma and blue naevi due to the similarities between the two.

Animal-type melanoma is generally excised, taking note of the clinical margin reliant on Breslow thickness. This is used as a prognostic factor in melanoma and provides a description of how deeply tumor cells have invaded.{{cite journal |last1=Breslow |first1=Alexander |year=1970 |title=Thickness, Cross-Sectional Areas and Depth of Invasion in the Prognosis of Cutaneous Melanoma |journal=Annals of Surgery |volume=172 |issue=5 |pages=902–8 |doi=10.1097/00000658-197011000-00017 |pmc=1397358 |pmid=5477666}}

Melanoma staging is the process of finding out if the melanoma has spread and if so, how far. This assists professionals in determining the intensity of the cancer and allows them to develop the best approach for treatment.{{Cite web |title=Stages of Melanoma Skin Cancer |url=https://www.cancer.org/cancer/melanoma-skin-cancer/detection-diagnosis-staging/melanoma-skin-cancer-stages.html |access-date=2023-03-19 |website=www.cancer.org |language=en}} Most melanoma specialists coincide with the American Joint Committee on Cancer (AJCC) for cutaneous melanoma staging guidelines:

• Balloon cell nevus
• List of cutaneous conditions

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Category:Melanoma