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PATIENT STORY

A 71-year-old woman presented with a rapidly growing lesion on her face over the past 4 months (Figure 174-1). The lesion had features of a basal cell carcinoma with a pearly border and telangiectasias (Figure 174-2). Also, the central crater with keratin gave it the appearance of a keratoacanthoma (KA). A shave biopsy was performed, and the pathology showed squamous cell carcinoma (SCC)–KA type. A full elliptical excision with 4-mm margins was then performed.

FIGURE 174-1

Pearly keratoacanthoma with telangiectasias and a central keratin core on the face of a 71-year-old woman. (Reproduced with permission from Richard P. Usatine, MD.)

FIGURE 174-2

Close-up of the keratoacanthoma with telangiectasias and a central keratin core on the face of the woman in Figure 174-1. (Reproduced with permission from Richard P. Usatine, MD.)

INTRODUCTION

The KA is a unique epidermal tumor characterized by rapid, abundant growth and a spontaneous resolution, with the classic presentation in middle-aged, light-skinned individuals in hair-bearing, sun-exposed areas. In the late 1940s, Freudenthal of Wroclaw coined the term keratoacanthoma, owing to the considerable acanthosis observed in the tumor. Controversies have arisen since the 1950s about the real nature of the tumor; some KAs may metastasize, and there is still debate over the relationship to SCC.1,2 With the current genetic and immunohistochemical data, many authors classify this tumor as a subtype of SCC.3

SYNONYMS

Self-healing squamous cell carcinoma1.

EPIDEMIOLOGY

  • KA develops as a solitary nodule in sun-exposed areas.

  • Seen more commonly later in life with a predilection for males.1

  • Develops rapidly within 6 to 8 weeks.

  • May spontaneously regress after 3 to 6 months or may continue to grow and rarely metastasize.

  • It is commonly underdiagnosed due to rapid growth and spontaneous regression.1

ETIOLOGY AND PATHOPHYSIOLOGY

  • KAs share features such as infiltration and cytologic atypia with SCCs.

  • KAs have been reported to metastasize.4

  • KA is considered to be a variant of SCC, called SCC-KA type.

  • Current histologic criteria categorized KA as well-differentiated SCC5; needs to correlate with clinical presentation.

  • In the majority of cases, KA originates from hair follicles, mainly from isthmus and infundibulum portion.1,6 This factor in part explains why KAs behave in a triphasic pattern: rapid growth, stabilization, and regression.1,6,7

RISK FACTORS

  • Age greater than 40.

  • Sun-exposed skin.

  • Light complexion.

  • Male gender.

  • Tattoos. KAs can develop in a new tattoo. Case reports reveal red ink is the most common cause.8

  • Medications such as azathioprine, ...

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