Advances in histopathological diagnosis of keratoacanthoma

Keratoacanthoma is a common epithelial lesion, but its nature is controversial. Although a distinct crateriform appearance is a hallmark of keratoacanthoma, other benign or malignant skin lesions may show a similar architecture. Moreover, as lesions diagnosed as conventional keratoacanthoma may show malignant behavior, some authors consider keratoacanthoma to be a variant of squamous cell carcinoma, whereas others consider it as a distinct self-resolving squamous proliferative lesion. The controversy seems to originate from the diverse behavior of keratoacanthoma-like epithelial lesions. However, a reproducible histopathological classification criterion has been recently proposed in the diagnosis of keratoacanthoma-like epithelial lesions, and its validity is supported by several reports that deal with the natural course or molecular aspects of these lesions. This article attempts to provide a comprehensive review on recent insights and advances in the histopathological diagnosis of keratoacanthoma or related lesions, as well as summary of related published works.