II. Epidemiology

  1. Onset later in life

III. Pathophysiology

  1. Squamoproliferative, benign epithelial lesions
  2. No longer thought to be associated with malignancy
    1. Not a squamous cell cancer variant
    2. May be difficult to distinguish from SCC (see below)

IV. Risk Factors

  1. Ultraviolet light exposure
  2. Human Papillomavirus
  3. Coal tar derivative exposure
  4. Cigarette smoking
  5. Chemical carcinogens

V. Signs

  1. Characteristics
    1. First
      1. Red to skin-colored firm, round Papule
      2. Rapid growth into dome-shaped Nodule
        1. May reach up to 1-2 cm in size within weeks to months
      3. Central umbilicated keratinous core
      4. Smooth surface
    2. Later (after 4-6 months)
      1. Lesion regresses over months
      2. Keratin core expelled
      3. Hypopigmented scar remains
  2. Distribution (sun-exposed areas)
    1. Face
    2. Extremities

VI. Differential Diagnosis

  1. Squamous Cell Skin Cancer
    1. Similar grossly and histologically to Keratoacanthoma

VII. Labs: Biopsy

  1. Biopsy lesions suspicious for Squamous Cell Skin Cancer (especially larger lesions)
    1. Exam and pathology findings can not always reliably distinguish keratocanthoma from SCC
    2. Complete excision with 3-5 mm margins is preferred overall
    3. Punch Biopsy is preferred over Shave Biopsy (depth may be inadequate otherwise)

VIII. Management

  1. Small Keratoacanthoma
    1. Electrodessication and Curettage
    2. Blunt Dissection
  2. Larger Keratoacanthoma
    1. Excision with 3-5 mm margins
    2. Moh's Surgery for difficult areas (esp. in regions with cosmetic concerns)
  3. Other options (non-surgical candidates, multiple lesions, inoperable skin sites)
    1. Topical agents
      1. 5-Fluorouracil 5% cream
        1. Apply during rapid growth tid
        2. Use under tape Occlusion
        3. Effective in 1-6 weeks
      2. Podophyllum 25% in benzoin
        1. Remove central crust and apply every 2 weeks prn
        2. Apply in clinic only due to high concentration
    2. Intralesional injections during rapid growth phase
      1. 5-Fluorouracil intralesional injection
      2. Methotrexate intralesional injection
      3. 5-Interferon alfa-2a injection
    3. Oral agents (for multiple lesions)
      1. Isotretinoin (Accutane)
    4. Radiotherapy
      1. Indicated for difficult cosmetic areas

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Related Studies

Ontology: keratoacanthoma (C0022572)

Definition (NCI) A dome-shaped, rapidly growing skin lesion composed of well differentiated squamous cells. It represents a proliferation of the infundibular epithelium of the hair follicle and its morphologic distinction from a well differentiated carcinoma may be difficult or impossible. Keratoacanthomas affect males more frequently than females and the majority tend to regress spontaneously. It has been suggested that keratoacanthoma represents a distinct subtype of squamous cell carcinoma of the skin.
Definition (NCI_CDISC) An epithelial skin neoplasm, composed of squamous cells, for which the malignancy status has not been established.
Definition (NCI_NCI-GLOSS) A rapidly growing, dome-shaped skin tumor that usually occurs on sun-exposed areas of the body, especially around the head and neck. Keratoacanthoma occurs more often in males. Although in most patients it goes away on its own, in a few patients it comes back. Rarely, it may spread to other parts of the body.
Definition (CSP) benign papular lesion with a superficial crater filled with a keratin plug, usually on the face.
Definition (MSH) A benign, non-neoplastic, usually self-limiting epithelial lesion closely resembling squamous cell carcinoma clinically and histopathologically. It occurs in solitary, multiple, and eruptive forms. The solitary and multiple forms occur on sunlight exposed areas and are identical histologically; they affect primarily white males. The eruptive form usually involves both sexes and appears as a generalized papular eruption.
Concepts Neoplastic Process (T191)
MSH D007636
SnomedCT 201061007, 201064004, 58220003, 156395005, 267858008, 254662007
English Keratoacanthoma, KERATOACANTHOMA, keratoacanthoma (diagnosis), Keratoacanthoma [Disease/Finding], keratoacanthomas, Keratoacanthoma (morphologic abnormality), Squamous cell carcinoma, keratoacanthoma-type, Keratoacanthomas, KERATOACANTHOMA, UNDETERMINED, Molluscum sebaceum, KA - Keratoacanthoma, Keratoacanthoma (disorder), Keratoacanthoma, NOS, keratoacanthoma
French KERATOACANTHOME, Cancer épidermoïde, type kérato-acanthome, Kératoacanthome, Kérato-acanthome
Spanish QUERATOACANTOMA, queratoacantoma localizado, queratoacantoma (anomalía morfológica), Carcinoma de células escamosas, tipo queratoacantoma, molusco sebáceo, queratoacantoma (trastorno), queratoacantoma, Queratoacantoma
German KERATOAKANTHOM, Plattenepithelkarzinom, Keratoacanthom-Typ, Keratoakanthom
Japanese ケラトアカントーマ, ケラトアカントーマ, ユウキョクサイボウガンケラトアカントーマガタ, 有棘細胞癌、ケラトアカントーマ型
Swedish Keratoakantom
Czech keratoakantom, Keratoakantom, Dlaždicobuněčný karcinom, typ keratoakantom
Finnish Keratoakantooma
Portuguese QUERATOACANTOMA, Carcinoma pavimentocelular, tipo queratoacantoma, Queratoacantoma, Ceratoacantoma
Polish Rogowiak kolczystokomórkowy
Hungarian Keratoacanthoma, Squamosus sejtes carcinoma, keratoacanthoma-típusú
Norwegian Keratoakantom
Dutch squameuscelcarcinoom, keratoacanthoom-type, keratoacanthoom, Acanthoom, kerato-, Keratoacanthoom
Italian Carcinoma a cellule squamose tipo cheratoacantoma, Cheratoacantoma