Solitary keratoacanthoma
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Keratoacanthoma (KA) is a common low-grade (unlikely to metastasize or invade) rapidly-growing skin tumour that is believed to originate from the hair follicle (
pilosebaceous unit A sebaceous gland is a microscopic exocrine gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin of mammals. In humans, sebaceous glands occur in the greatest number ...
) and can resemble
squamous cell carcinoma Squamous-cell carcinomas (SCCs), also known as epidermoid carcinomas, comprise a number of different types of cancer that begin in squamous cells. These cells form on the surface of the skin, on the lining of hollow organs in the body, and on the ...
. The defining characteristic of a keratoacanthoma is that it is dome-shaped, symmetrical, surrounded by a smooth wall of inflamed skin, and capped with
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
scales and debris. It grows rapidly, reaching a large size within days or weeks, and if untreated for months will almost always starve itself of nourishment,
necrose Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
(die), slough, and heal with scarring. Keratoacanthoma is commonly found on sun-exposed skin, often face, forearms and hands. It is rarely found at a
mucocutaneous junction A mucocutaneous junction, or mucocutaneous boundary, is a region of the body in which mucosa transitions to skin. Mucocutaneous zones occur in animals, at the body orifices. In humans, mucocutaneous junctions are found at the lips, nostrils, conju ...
or on
mucous membranes A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...
. Keratoacanthoma may be difficult to distinguish visually from a skin cancer. Under the microscope, keratoacanthoma very closely resembles
squamous cell carcinoma Squamous-cell carcinomas (SCCs), also known as epidermoid carcinomas, comprise a number of different types of cancer that begin in squamous cells. These cells form on the surface of the skin, on the lining of hollow organs in the body, and on the ...
. In order to differentiate between the two, almost the entire structure needs to be removed and examined. While some pathologists classify keratoacanthoma as a distinct entity and not a malignancy, about 6% of clinical and histological keratoacanthomas do progress to invasive and aggressive squamous cell cancers; some pathologists may label KA as "well-differentiated squamous cell carcinoma, keratoacanthoma variant", and prompt definitive surgery may be recommended.


Classification

Frequently reported and reclassified over the last century, keratoacanthoma can be divided into various subtypes and despite being considered benign, their unpredictable behaviour has warranted the same attention as with squamous cell carcinoma. Keratoacanthomas may be divided into the following types:Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McGraw-Hill. .James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatology''. (10th ed.). Saunders. . * ''Giant keratoacanthomas'' are a variant of keratoacanthoma, which may reach dimensions of several centimeters. * ''Keratoacanthoma centrifugum marginatum'' is a cutaneous condition, a variant of keratoacanthomas, which is characterized by multiple tumors growing in a localized area. * ''Multiple keratoacanthomas'' (also known as "Ferguson–Smith syndrome," "Ferguson-Smith type of multiple self-healing keratoacanthomas,") is a cutaneous condition, a variant of keratoacanthomas, which is characterized by the appearance of multiple, sometimes hundreds of keratoacanthomas. * A ''solitary keratoacanthoma'' (also known as "Subungual keratoacanthoma") is a benign, but rapidly growing, locally aggressive tumor which sometimes occur in the nail apparatus. * ''Generalized eruptive keratoacanthoma'' (also known as "Generalized eruptive keratoacanthoma of Grzybowski") is a cutaneous condition, a variant of keratoacanthomas, characterized by hundreds to thousands of tiny follicular keratotic
papule A papule is a small, well-defined bump in the skin. It may have a rounded, pointed or flat top, and may have a dip. It can appear with a stalk, be thread-like or look warty. It can be soft or firm and its surface may be rough or smooth. Some h ...
s over the entire body. Treatments are not successful for many people with generalized eruptive keratoacanthoma. Use of emollients and anti-itch medications can ease some symptoms. Improvement or complete resolutions of the condition has occurred with the application of the following medications:
acitretin Acitretin (trade names Soriatane and Neotigason) is a second-generation retinoid. It is taken orally, and is typically used for psoriasis. Acitretin is an oral retinoid used in the treatment of severe resistant psoriasis. Because of the potential ...
,
isotretinoin Isotretinoin, also known as 13-''cis''-retinoic acid and sold under the brand name Accutane among others, is a medication primarily used to treat severe acne. It is also used to prevent certain skin cancers (squamous-cell carcinoma), and in th ...
,
fluorouracil Fluorouracil (5-FU), sold under the brand name Adrucil among others, is a cytotoxic chemotherapy medication used to treat cancer. By intravenous injection it is used for treatment of colorectal cancer, oesophageal cancer, stomach cancer, pan ...
,
methotrexate Methotrexate (MTX), formerly known as amethopterin, is a chemotherapy agent and immune-system suppressant. It is used to treat cancer, autoimmune diseases, and ectopic pregnancies. Types of cancers it is used for include breast cancer, leuke ...
,
cyclophosphamide Cyclophosphamide (CP), also known as cytophosphane among other names, is a medication used as chemotherapy and to suppress the immune system. As chemotherapy it is used to treat lymphoma, multiple myeloma, leukemia, ovarian cancer, breast cancer ...
.


Cause

Keratoacanthomas usually occurs in older individuals. A number of causes have been suggested including
ultraviolet light Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
, chemical
carcinogens A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...
, recent injury to the skin,
immunosuppression Immunosuppression is a reduction of the activation or efficacy of the immune system. Some portions of the immune system itself have immunosuppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse react ...
and
genetic predisposition A genetic predisposition is a genetic characteristic which influences the possible phenotypic development of an individual organism within a species or population under the influence of environmental conditions. In medicine, genetic susceptibilit ...
. As with squamous cell cancer, sporadic cases have been found co-infected with the
human papilloma virus Human papillomavirus infection (HPV infection) is caused by a DNA virus from the ''Papillomaviridae'' family. Many HPV infections cause no symptoms and 90% resolve spontaneously within two years. In some cases, an HPV infection persists and res ...
(HPV).Niebuhr M, et al. Giant keratoacanthoma in an immunocompetent patient with detection of HPV 11. Hautarzt. 2009; 60(3):229–32 () Although HPV has been suggested as a causal factor, it is unproven. Many new treatments for melanoma are also known to increase the rate of keratoacanthoma, such as the BRAF inhibitor medications
vemurafenib Vemurafenib (INN, marketed as Zelboraf) is an inhibitor of the B-Raf enzyme developed by Plexxikon (now part of Daiichi-Sankyo) and Genentech for the treatment of late-stage melanoma.; The name "vemurafenib" comes from V600E mutated BRAF in ...
and
dabrafenib Dabrafenib, sold under the brand name Tafinlar & Rafinlar ( both by Novartis) among others, is a medication for the treatment of cancers associated with a mutated version of the gene BRAF. Dabrafenib acts as an inhibitor of the associated enzym ...
.


Diagnosis

Keratoacanthomas presents as a fleshy, elevated and nodular lesion with an irregular crater shape and a characteristic central hyperkeratotic core. Usually the people will notice a rapidly growing dome-shaped tumor on sun-exposed skin. If the entire lesion is removed, the pathologist will probably be able to differentiate between keratoacanthoma and squamous cell carcinoma. Follow-up would be required to monitor for recurrence of disease.


Treatment

Excision of the entire lesion, with adequate margin, will remove the lesion, allow full tissue diagnosis, and leave a planned surgical wound which can usually be repaired with a good cosmetic result. However, removing the entire lesion (especially on the face) may present difficult problems of plastic reconstruction. (On the nose and face,
Mohs surgery Mohs surgery, developed in 1938 by a general surgeon, Frederic E. Mohs, is microscopically controlled surgery used to treat both common and rare types of skin cancer. During the surgery, after each removal of tissue and while the patient waits, t ...
may allow for good margin control with minimal tissue removal, but many insurance companies require the definitive diagnosis of a malignancy ''before'' they are prepared to pay the extra costs of Mohs surgery.) Especially in more cosmetically-sensitive areas, and where the clinical diagnosis is reasonably certain, alternatives to surgery may include no treatment (awaiting spontaneous resolution).Keratoacanthoma. Désirée Ratner. 2004. http://www.medscape.com/viewarticle/467069 accessed 23 June 2015 On the trunk, arms, and legs,
electrodesiccation Cauterization (or cauterisation, or cautery) is a medical practice or technique of burning a part of a body to remove or close off a part of it. It destroys some tissue in an attempt to mitigate bleeding and damage, remove an undesired growth, or ...
and
curettage Curettage ( or ), in medical procedures, is the use of a curette (French, meaning scoopMosby's Medical, Nursing & Allied Health Dictionary, Fourth Edition, Mosby-Year Book 1994, p. 422) to remove tissue by scraping or scooping. Curettages are ...
often suffice to control keratoacanthomas until they regress. Other modalities of treatment include
cryosurgery Cryosurgery is the use of extreme cold in surgery to destroy abnormal or diseased tissue; thus, it is the surgical application of cryoablation. The term comes from the Greek words cryo (κρύο) ("icy cold") and surgery (''cheirourgiki'' – χ ...
and
radiotherapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...
; intralesional injection of
methotrexate Methotrexate (MTX), formerly known as amethopterin, is a chemotherapy agent and immune-system suppressant. It is used to treat cancer, autoimmune diseases, and ectopic pregnancies. Types of cancers it is used for include breast cancer, leuke ...
or
5-fluorouracil Fluorouracil (5-FU), sold under the brand name Adrucil among others, is a cytotoxic chemotherapy medication used to treat cancer. By intravenous injection it is used for treatment of colorectal cancer, oesophageal cancer, stomach cancer, pancrea ...
have also been used. Recurrence after electrodesiccation and curettage can occur; it can usually be identified and treated promptly with either further curettage or surgical excision.


History

In 1889, Sir
Jonathan Hutchinson Sir Jonathan Hutchinson (23 July 1828 – 23 June 1913), was an English surgeon, ophthalmologist, dermatologist, venereologist, and pathologist. Life He was born in Selby, Yorkshire, of Quaker parents and educated in the local school. Then he ...
described a crateriform ulcer on the face”. In 1936, the same condition was renamed "molluscum sebaceum" by MacCormac and Scarf. Later, the term “keratoacanthoma” was coined by
Walter Freudenthal Walter Freudenthal (6 May 1893 – 27 March 1952) was a German-Jewish dermatologist who gave the earliest clear histopathological description of keratoma senile (actinic keratosis) in 1926 in Breslau. In 1933, he moved to London to escape the N ...
and the term became established by
Arthur Rook Arthur Rook may refer to: * Arthur Rook (equestrian) (1921–1989), English equestrian and Olympic champion * Arthur Rook (dermatologist) (1918–1991), British dermatologist and author See also * Arthur Rooke (fl. 1910s–1920s), British a ...
and pathologist Ian Whimster in 1950.


See also

*
List of cutaneous conditions Many skin conditions affect the human integumentary system—the organ system covering the entire surface of the body and composed of skin, hair, nails, and related muscle and glands. The major function of this system is as a barrier against t ...
* Marian Grzybowski


References


External links

{{Skin tumors, epidermis Epidermal nevi, neoplasms, and cysts