The many faces of keratoacanthomas

Keratoacanthoma: hyperplasia, benign neoplasm, or a type of squamous cell carcinoma?

Keratoacanthomas are common self limited squamous proliferations. They have been considered a benign neoplasm with involution and complete resolution within few months. Although considered the prototypical example of cutaneous pseudomalignancy, some believe that these tumors are squamous cell carcinomas and through the years there have been sporadic reports of "metastasizing keratoacanthomas". The question has been raised as to whether keratoacanthoma is an unreliable histological diagnosis or these tumors have a latent, albeit rare, malignant potential. To date, just a handful of "metastasizing keratoacanthomas" have been reported. Since a benign lesion is incapable of metastasis, some other explanation must be considered; the most likely one being a misdiagnosis. While it is clear that in some cases, the histological and cytological features of squamous cell carcinoma and keratoacanthoma are difficult to distinguish by current techniques, these occasional limitations in diagnosis do not make keratoacanthomas a carcinoma. We believe the evidence supports that keratoacanthomas are benign squamous proliferations. The diagnosis can be made with confidence in appropriate biopsies and using well established clinicopathological criteria.

The regressing keratoacanthoma

The clinical and pathological features of 11 cases of regressing keratoacanthoma are presented. These lesions were from sun-exposed skin of individuals between the ages of 58 and 92 years and were of short clinical duration (2-12 months). Histologically, these lesions showed similar features and consisted of symmetrical shallow cup-shaped invaginations of thin atrophic epidermis with overhanging edges. The underlying papillary dermis demonstrated variable degrees of inflammatory infiltrate and scarring. It is important to recognize these features as representing regressed keratoacanthoma as they may be confused with other unrelated skin conditions.

Surgical treatment for aggressive giant keratoacanthoma of the face

A case of aggressive giant keratoacanthoma on the right temple region is described. Histopathologic examination was not definitive for keratoacanthoma, so that clinical considerations were helpful for diagnosis. The neoplasm was treated successfully with surgical excision and immediate repair with skin graft, in spite of one narrow peripheral area of residual disease on the wound surface after resection.