History

Fact Explanation
Skin swelling Keratoacanthoma is a benign epithelial neoplasm which originates in the epithelium of the hair follicle above the sebaceous glands. Sometimes it is considered as a form of squamous cell carcinoma. Keratoacanthoma grows rapidly over a few weeks to months, followed by a slow spontaneous resolution over 4 months to 1 year. The lesion mostly occurs on sun-exposed areas such as face, neck, and dorsum of hands and forearms. They are usually solitary and begin as firm, round, skin-coloured or reddish papule. This initial papule rapidly progresses to a dome-shaped nodules with a smooth shiny surface. [1,2,3,4,5]
Ulceration With time, the papule grows rapidly, reaching a large size within days or weeks. And then it begin to necrose resulting a central crater of ulceration. [1,4,5,]
Keratin horn Keratin plug may project like a horn instead of causing an ulceration. [2,3]
Scars If nor excised, the ulceration leaves a residual scar. [1,3]
Risk factors Presence of particular strains of the wart virus (human papillomavirus) that cause viral warts, frequent exposure to the Sunlight and chemical carcinogens, trauma, industrial workers exposed to pitch and tar, immuno-depletion , chronic ulcers and previous skin cancers are predisposing. Peak incidence occurs in those aged over 60 years. It is rare in young adults and in darker-skinned patients. Males are twice as often affected as females. [1,2,3,5,6]
References
  1. SAZAFI MS, SALINA H, ASMA A, MASIR N, PRIMUHARSA PUTRA SH. Keratoacanthoma: an unusual nasal mass. Acta Otorhinolaryngol Ital [online] 2013 Dec, 33(6):428-30 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/24376301
  2. ESPINOZA W, PEREZ C, CUEVAS P. Keratoacanthoma. BMJ Case Rep [online] 2009 [viewed 18 August 2014] Available from: doi:10.1136/bcr.09.2008.0995
  3. JACKSON R. Keratoacanthoma. Can Med Assoc J [online] 1959 Apr 1, 80(7):551-2 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/20325906
  4. JACKSON R, WILLIAMSON GS. Keratoacanthoma: incidence and problems in diagnosis and treatment. Can Med Assoc J [online] 1961 Feb 11:312-5 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/13718502
  5. PâRVăNESCU H, MOGOANTă L, FOARFă C, CIUREA M, GEORGESCU A, NICOLAE C. Giant keratoacanthoma of the hand. Rom J Morphol Embryol [online] 2005, 46(3):235-8 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/16444311
  6. NGO J, BARANKIN B. Dermacase. Keratoacanthoma. Can Fam Physician [online] 2008 Jul, 54(7):985, 993 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/18625820

Examination

Fact Explanation
Papule The initial lesion is a firm, symmetrically round/ dome-shaped papule. The lesion is usually solitary. And the surface is skin colored or inflamed (reddish). Common sites include Neck Face, and dorsum of the upper extremities. [1,2,3,4]
Nodule The initial papule rapidly develops in to a dome-shaped nodules with a smooth shiny surface. [2,4]
Ulcer In later presentation, ulcer can be observed. It enlarges up to 2cm in diameter. The middle of the nodule become ulcerated like a crated. Or a keratin plug appears that may develop into a horn like structure. [1,2,3]
References
  1. PâRVăNESCU H, MOGOANTă L, FOARFă C, CIUREA M, GEORGESCU A, NICOLAE C. Giant keratoacanthoma of the hand. Rom J Morphol Embryol [online] 2005, 46(3):235-8 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/16444311
  2. ESPINOZA W, PEREZ C, CUEVAS P. Keratoacanthoma. BMJ Case Rep [online] 2009 [viewed 18 August 2014] Available from: doi:10.1136/bcr.09.2008.0995
  3. JACKSON R. Keratoacanthoma. Can Med Assoc J [online] 1959 Apr 1, 80(7):551-2 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/20325906
  4. JACKSON R, WILLIAMSON GS. Keratoacanthoma: incidence and problems in diagnosis and treatment. Can Med Assoc J [online] 1961 Feb 11:312-5 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/13718502

Differential Diagnoses

Fact Explanation
Squamous Cell Carcinoma Squamous cell carcinoma (SCC) is a common type of skin cancer. It is derived from squamous cells, the flat cells that make up the outside layers of the skin, the epidermis. These cells are keratinising i.e., they produce keratin, the horny protein that makes up skin, hair and nails. Invasive SCC refers to cancer cells that have grown into the deeper layers of the skin, the dermis. Invasive SCC can rarely metastasize. Invasive SCCs are usually slowly-growing, tender, scaly or crusted lumps. The lesions may develop sores or ulcers that fail to heal. Most SCCs are found on sun-exposed sites, particularly the face, lips, ears, hands, forearms and lower legs. [1]
Cutaneous Horn Cutaneous horns, also known by the Latin name cornu cutaneum, are unusual keratinous skin tumors with the appearance of horns. Cutaneous horns generally present as curved hard yellow brown horns. They can be surrounded by normal skin or have a border of thickened skin. The side of the horn may be terrace-like with horizontal ridges. The base of the horn may be flat, protruding, or like a crater. Inflammation may be present, due to recurrent injury. [2]
Actinic Keratosis This is a UV light–induced lesion which can progress to an invasive squamous cell carcinoma of the skin. It is a common lesion with malignant potential which arise on the skin by far. Multiple lesions may develop within a single anatomic area, in patients to an extent where the lesions collide to produce a relatively large area with confluent actinic keratosis. [3]
References
  1. AWAN BA, ALZANBAGI H, SAMARGANDI OA, AMMAR H. Scalp squamous cell carcinoma in xeroderma pigmentosum. N Am J Med Sci [online] 2014 Feb, 6(2):105-6 [viewed 04 August 2014] Available from: doi:10.4103/1947-2714.127754
  2. OLUDIRAN OO, EKANEM VJ. Cutaneous horns in an african population. J Cutan Aesthet Surg [online] 2011 Sep, 4(3):197-200 [viewed 19 August 2014] Available from: doi:10.4103/0974-2077.91253
  3. IANHEZ M, FLEURY LF JR, MIOT HA, BAGATIN E. Retinoids for prevention and treatment of actinic keratosis. An Bras Dermatol [online] 2013 Jul-Aug, 88(4):585-93 [viewed 19 August 2014] Available from: doi:10.1590/abd1806-4841.20131803

Investigations - for Diagnosis

Fact Explanation
Histopathology Specimen should be taken as excisional or deep incisional biopsy. Shave biopsy does not help to distinguish keratoacanthoma from invasive squamous cell carcinoma. There is a central plug of keratin producing an invagination of the epidermis. There is a collarette of epidermis at the lateral margin. The epithelium is proliferative but well differentiated, often with a ground glass appearance and marked keratinization. Thus the epithelium exhibiting pseudo-carcinomatous growth pattern. Connective tissue shows a moderate to marked infiltrate of chronic inflammatory cells. [1,2,3]
References
  1. SAZAFI MS, SALINA H, ASMA A, MASIR N, PRIMUHARSA PUTRA SH. Keratoacanthoma: an unusual nasal mass. Acta Otorhinolaryngol Ital [online] 2013 Dec, 33(6):428-30 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/24376301
  2. NGO J, BARANKIN B. Dermacase. Keratoacanthoma. Can Fam Physician [online] 2008 Jul, 54(7):985, 993 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/18625820
  3. PâRVăNESCU H, MOGOANTă L, FOARFă C, CIUREA M, GEORGESCU A, NICOLAE C. Giant keratoacanthoma of the hand. Rom J Morphol Embryol [online] 2005, 46(3):235-8 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/16444311

Management - Specific Treatments

Fact Explanation
Retinoids Though the definitive management of the condition, medical therapy is reserved for multiple lesions and ones which are not amenable to surgery owing to their size or location. Systemic retinoids, such as isotretinoin, are considered in such instances. [1,2]
Cryotherapy Small keratoacanthomas and lesions in difficult to treat locations are successfully treated with cryotherapy. [1,2,3,4]
Curettage On the trunk, arms, and legs, electrodesiccation and curettage often suffice. [1,3,5]
Excision Excision of the entire lesion is often required if one wants to confirm the clinical diagnosis of keratoacanthoma. [1,2,3]
Radiotherapy The lesions are radiosensitive and well respond to low doses of radiation. This may be useful in selected patients with large tumors while resection will result in cosmetic deformity and for tumor's that have recurred following attempted excision. [2,3,4,5]
References
  1. NGO J, BARANKIN B. Dermacase. Keratoacanthoma. Can Fam Physician [online] 2008 Jul, 54(7):985, 993 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/18625820
  2. SAZAFI MS, SALINA H, ASMA A, MASIR N, PRIMUHARSA PUTRA SH. Keratoacanthoma: an unusual nasal mass. Acta Otorhinolaryngol Ital [online] 2013 Dec, 33(6):428-30 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/24376301
  3. JACKSON R, WILLIAMSON GS. Keratoacanthoma: incidence and problems in diagnosis and treatment. Can Med Assoc J [online] 1961 Feb 11:312-5 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/13718502
  4. PâRVăNESCU H, MOGOANTă L, FOARFă C, CIUREA M, GEORGESCU A, NICOLAE C. Giant keratoacanthoma of the hand. Rom J Morphol Embryol [online] 2005, 46(3):235-8 [viewed 18 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/16444311
  5. ESPINOZA W, PEREZ C, CUEVAS P. Keratoacanthoma. BMJ Case Rep [online] 2009 [viewed 18 August 2014] Available from: doi:10.1136/bcr.09.2008.0995