Keratoacanthoma

ID: 68y/o ♂ came in due to a raised skin lesion on his Lt hand; 

HPI: pt noticed a small area of redness on the dorsal aspect of his Lt hand a few weeks ago; no other skin lesions; no Hx of similar lesions in the past; ROS noncontributory; 

SH: retired, used to work in the logging industry; non smoker; drinks ETOH socially; 

E/O: Looks well; VSSA;

A 1x1cm round nodule on the dorsal surface of the Lt hand; the lesion had a keratin filled central crater; mildly tender to touch; atrophic surrounding skin with mild erythema; no other skin lesions; 

A/P: Pros and cons of excisional Bx were discussed; pt was agreeable and was booked for the procedure; 

Discussion: 

Main DDx if SCC; Bx for definitive Dx and to differentiate from SCC; 

M>F; usually after the age of 50, but can occur at any age; rare below the age of 20; 

Has three stages of development as below,

1. proliferation: may last for 6-8wK; rapid growth to 1-2cm nodule; 
2. maturation: may last for several weeks to several mo; 
3. involution: may last for 4-6wk

First line of treatment is excisional Bx with a 4mm safe margin; Bx should extend to the subcutaneous fat;

KA usually goes through these 3 stages in 4-9mo; 

Referenced: 

1. http://www.uptodate.com/contents/keratoacanthoma-epidemiology-risk-factors-and-diagnosis?source=search_result&search=keratoacanthoma&selectedTitle=2%7E35
2. http://www.uptodate.com/contents/keratoacanthoma-management-and-prognosis?source=see_link
3. http://medicalpicturesinfo.com/wp-content/uploads/2011/09/Keratoacanthoma-2.jpg