A 60-year-old man comes to the physician because of concerns about a lesion on his leg. It first appeared 3 months ago and rapidly grew to its current size. For the past several weeks, it has been stable with no additional growth. There is no associated pain.
The lesion is shown in the photograph below.

What is the most likely diagnosis?

Question

A 60-year-old man comes to the physician because of concerns about a lesion on his leg.  It first appeared 3 months ago and rapidly grew to its current size.  For the past several weeks, it has been stable with no additional growth.  There is no associated pain.
The lesion is shown in the photograph below.

What is the most likely diagnosis?

Quizplus · Accepted Answer

This patient most likely has a keratoacanthoma (KA), a low-grade squamous cell carcinoma that usually develops on sun-exposed skin of middle-aged or elderly (usually fair-skinned) individuals. They are most commonly found on the central face, dorsal hands, arms, and legs. A distinguishing feature of KA is a clinical course characterized by rapid growth (several weeks), followed by a variable period of lesion stability (several months), and subsequent spontaneous resolution (several weeks). Classic examination reveals a solitary, dome-shaped, skin-colored nodule with a central hyperkeratotic, keratinous plug. Prior to their spontaneous involution, KAs can be difficult to distinguish clinically from squamous cell carcinoma, a lesion with a relatively greater risk for metastasis and death. Therefore, all lesions suspicious for KA should be biopsied. The recognition of both clinical and histopathologic features consistent with KA is used to make the diagnosis. (Choice A) The most common presentation of basal cell carcinoma is a slow-growing papule or nodule with a pearly, rolled border and overlying telangiectasia. Ulceration is commonly observed, as is bleeding following minor trauma. basal cell carcinoma (Choice C) Molluscum contagiosum is caused by poxvirus and is characterized by multiple small, dome-shaped papules with central umbilication. Molluscum contagiosum (Choice D) Prurigo nodules are cutaneous lesions that occur in chronically rubbed or scratched skin. Examination may reveal dome-shaped, firm papules and nodules (0.5-2 cm) that are eroded, ulcerated, and crusted. Prurigo nodules (Choice E) Pyogenic granuloma is a benign vascular tumor of the skin and mucosa that presents as an erythematous, dome-shaped papule that bleeds easily. The lesions frequently develop over a period of a few days to weeks. Pyogenic granuloma Educational objective: Keratoacanthoma presents as a solitary, dome-shaped nodule with a central hyperkeratotic, keratinous plug. These lesions grow rapidly over a 4- to 9-month period, stabilize, and spontaneously regress. Due to the difficulty of distinguishing KA clinically from squamous cell carcinoma, all lesions should be biopsied. __________ References: Keratoacanthoma: a clinicopathologic enigma. (http://www.ncbi.nlm.nih.gov/pubmed/14871228) Keratoacanthomas: overview and comparison between Houston and Minneapolis experiences. (http://www.ncbi.nlm.nih.gov/pubmed/20214172)

A 60-Year-Old Man Comes to the Physician Because of Concerns