Keratoacanthoma is a dome-shaped lump or tumor that grows on your skin. Once you spot it, it’s important to talk to your doctor. It sometimes happens to people before they get squamous
cell carcinoma, the second most common type of skin cancer. If you catch the problem early, treatment usually works well. You might think you have a pimple or boil at first, but
keratoacanthoma can grow fast and get as big as a quarter in a couple of months. It looks like a small, red or skin-colored volcano -- there’s a distinctive crater at the top of the lump that often has keratin, or dead skin cells, inside. You’ll usually see keratoacanthoma on skin that’s been exposed to the sun, like your head, neck, arms, the backs of your hands, and sometimes your legs. It often starts in a
hair follicle. Men are twice as likely to have the condition as women. It’s also more common for white people than those with darker skin and in people age 60 and over. It’s rare for anyone under age 20 to have keratoacanthoma. Doctors don’t know what causes keratoacanthoma,
but some things make you more likely to get it: Your doctor will probably take a biopsy, or a piece of the tumor, to send to an expert called a pathologist, who will examine the sample under a
microscope. The cells of keratoacanthoma often look just like those of squamous cell carcinoma. Your doctor will have to remove a large-enough piece so the pathologist can see the shape of the tumor with its distinctive crater. The most common treatment is surgery to remove the keratoacanthoma. You can have the procedure in your doctor’s office with medicine to numb the area around the tumor. There
are a few different surgeries your doctor may use. They can: If you can’t have
surgery, or if you have multiple keratoacanthomas, you can try other treatments: It’s not unusual for a single keratoacanthoma to shrink and disappear
on its own after several months. But it may leave a worse scar than one from surgery. It could also come back, so it’s best to get it removed. If you don’t treat it, keratoacanthoma can spread throughout your body. Once you’ve had one keratoacanthoma, you may be more likely to get others in the future. Check your skin regularly for any lumps or unusual spots, and see your doctor for a full-body exam twice a year. It’s
also important to protect your skin from sun damage. These conditions are extremely rare, but they can cause multiple keratoacanthomas to grow on your skin. There can be so many that doctors can’t remove them all with surgery. Ferguson-Smith. This can cause as many as 100 keratoacanthomas at one time. It’s the most common type of multiple keratoacanthoma. It’s a condition you
can get through your genes and may start as early as age 8. You may take retinoid medicine to try to reduce the number of additional tumors. Grzybowski syndrome is even more rare. It causes tumors that are smaller but
itch intensely. They may even show up in the mouth.Symptoms
Who Gets Keratoacanthoma?
Getting a Diagnosis
Treatments for Keratoacanthoma
Prevention
Conditions Related to Keratoacanthoma
Skin nonmelanocytic tumor
Carcinoma (nonadnexal)
Keratoacanthoma / SCC keratoacanthoma type
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Definition / general
- Keratoacanthoma (KA) is a well differentiated, cutaneous squamous cell carcinoma, which often spontaneously regresses
- Regression is thought to be due to immune mediated destruction of squamous cells
- For lesions that are entirely resected, can diagnose as "well differentiated squamous cell carcinoma, keratoacanthoma type”
- For lesions that are not entirely histologically examined, can diagnose as "well differentiated squamous cell carcinoma with features of keratoacanthoma”
Essential features
- Common, represents approximately up to 30% of cases of cutaneous squamous cell carcinoma (SCC)
- Dome shaped tumor with central keratinous plug in sun exposed areas
- May become large, up to 10 cm (called giant KA)
- Good prognosis; vast majority of cases spontaneously regress
Terminology
- Agglomerate KA (variant)
- KA centrifugum (variant)
- Giant KA (variant)
- Subungual KA (variant)
- Intraoral KA (variant)
ICD coding
- ICD-O: 8071/3 - keratoacanthoma, NOS
- ICD-10: L85.8 - other specified epidermal thickening
- ICD-11: 2F72 - neoplasms of uncertain behavior of skin
Sites
- Head and neck most common sites, followed by extremities (Open Access Maced J Med Sci 2018;6:531)
Pathophysiology
- Tumor stems from follicular infundibulum related to chronic solar (UV) damage (Indian J Dermatol 2011;56:435)
- Undergoes 3 clinical stages: proliferative, mature, involutional / resolving (Arch Craniofac Surg 2015;16:92)
Diagnosis
- Excisional biopsy preferred to show suggestive histopathology
Prognostic factors
- Nonfatal tumor
- Can regress; however, final size prior to regression is difficult to predict (J Am Acad Dermatol 2016;74:1220)
- Recurrence is uncommon with surgical removal
- Self limited proliferation with low probability of malignant transformation (more often associated with perineural invasion) (Acta Biomed 2019;90:580)
Case reports
- 56 year old man with giant variant keratoacanthoma of the cheek (Arch Craniofac Surg 2015;16:92)
- 61 year old man with rapidly occurring forearm keratoacanthoma over 11 days (Cutis 2015;95:E7)
- 74 year old man with keratoacanthoma of the palm (Cureus 2018;10:e2331)
- 79 year old man with keratoacanthoma of the forehead with venous invasion (Dermatol Pract Concept 2012;2:204a03)
- 92 year old man with keratoacanthoma of the left cheek with perineural invasion (Acta Biomed 2019;90:580)
Treatment
- Monitoring for spontaneous regression; often leaves atrophic hypopigmented scar (Indian J Dermatol 2011;56:435)
- Typically treated with complete surgical excision; Mohs surgery performed dependent on location (Ann Dermatol 2011;23:357)
- Electrosurgery, cryosurgery, laser surgery, systemic or topical chemotherapy occasionally utilized (J Dent (Shiraz) 2014;15:91)
- Radiotherapy can be utilized with reoccurrence or potential large cosmetic disfigurement with surgery; typically not utilized in young adult patients (J Am Acad Dermatol 1990;23:489)
Clinical images
Images hosted on other servers:
Large face tumor
Palm tumor
Forehead lesion
Gross description
- Typically large, scaly, dome shaped tumor with central keratinous plug
Microscopic (histologic) description
- Low power magnification shows large, well differentiated squamous tumor with central keratin filled crater
- Surrounding epidermis forms a lip around the invaginating crateriform tumor
- Tumor is composed of bland squamous cells with abundant eosinophilic or glassy cytoplasm and enlarged hyperchromatic to vesicular appearing nuclei
- Mitotic activity and cellular atypia are usually seen at the periphery of tumor
- Intraepidermal neutrophilic microabscesses and keratin horn pearls are seen within the tumor
- Regressing tumors show epidermal atrophy, bland cytologic features, dermal inflammation and fibrosis at the periphery of tumor
Microscopic (histologic) images
Contributed by Poonam Sharma, M.B.B.S.
Central crater
Bland squamous cells
Whorl of laminated keratin
Virtual slides
Images hosted on other servers:
Invaginated, keratin filled tumor
Molecular / cytogenetics description
- Transforming growth factor beta receptor 1 can cause multiple self healing squamous epithelioma (MMSE); most common cause of multiple KA
- Germline mutations of hMSH2 and hMLH1 mismatch repair genes causing Muir-Torre syndrome have been implicated in solitary and multiple KA formation
- BRAF kinase inhibitors utilized to treat KA has been reported to induce reactive KA by paradoxical activation of the ERK MAPkinase pathway
- Reference: Exp Dermatol 2016;25:85
Videos
Keratoacanthoma
Sample pathology report
- Skin, left cheek (clinical keratoacanthoma), excision:
- Well differentiated squamous cell carcinoma, keratoacanthoma type (see comment)
- Comment: Well differentiated hyperplastic squamous epithelium with crater-like depression with keratin horn pearls present centrally. Enlarged hyperchromatic vesicular nuclei present along with glassy appearing cytoplasm.
Differential diagnosis
- Conventional, well differentiated squamous cell carcinoma:
- Shows greater cellular atypia and mitotic activity
- Intraepidermal neutrophilic microabscesses and tissue eosinophilia less common
- May be difficult to distinguish in superficial biopsies
- Verrucous carcinoma:
- Shows prominent endophytic and exophytic growth
- Lacks central crateriform architecture
- Also has bland cytologic features
- May be difficult to distinguish in superficial biopsies
Board review style question #1
A 62 year old man presents with a single, solitary, skin colored tumor that has a crater-like appearance with central keratin buildup on his left forearm. It appeared spontaneously and has grown rapidly over the past 3 weeks. It is painless to the touch but is cosmetically displeasing. He has no other skin conditions. The tumor is excised and a microscopic image is shown above. Which of the following is true concerning this skin lesion?
- It is a variant of basal cell carcinoma
- The underlying cause for this tumor is typically due to a genetic mutation
- The malignant potential of this tumor is high and it must be removed immediately
- This tumor has the potential to completely spontaneously regress
Board review style answer #1
D. This tumor has the potential to completely spontaneously regress. This is a well differentiated squamous cell carcinoma, keratoacanthoma type.
Comment Here
Reference: Keratoacanthoma
Board review style question #2
A 70 year old male farmer presents with a skin tumor on his cheek that has grown quickly over the past month. It has a crater-like appearance without arborizing telangiectasias on dermatoscopy. Biopsy shows that the tumor is mainly composed of bland squamous cells with intraepidermal neutrophilic microabscesses and keratin horn pearls under the microscope. Which of the following is true concerning this skin tumor?
- Peripheral palisading and clefting are also likely to be seen under the microscope
- It has overlapping features of squamous cell carcinoma
- Due to its rapid growth, this tumor is likely to metastasize
- Excessive UV damage plays no role in pathogenesis
Board review style answer #2
B. It has overlapping features of squamous cell carcinoma. The lesion is a keratoacanthoma.
Comment Here
Reference: Keratoacanthoma
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