Solitary Palmar Keratoacanthoma: Case Report

Abstract

Keratoacanthoma (KA) is a squamous neoplasm exhibiting a triphasic growth pattern involving rapid growth, stabilization, and eventual spontaneous resolution. Historically, keratoacanthomas were thought to originate on hair-bearing skin or sun-exposed surfaces. However, recent reports demonstrate that they can occur on the mucous membranes, subungual regions, and palms and soles. We report a 74-year-old man who developed a KA on the left palmar surface after minor trauma, for which he underwent Mohs' micrographic surgery. A literature review for the terms: keratoacanthoma, palm, palmar, volar, plantar, and sole resulted in only four reported cases of solitary or giant KA of the palms and soles; excluding our patient, all of the cases occurred on the plantar foot. A number of reports describe palmar KA in the context of multiple lesions occurring simultaneously. However, to our knowledge, our patient represents the first reported case of a solitary palmar KA in the literature. The features of follicular and non-follicular keratoacanthomas (KAs) and their association with trauma are discussed.

Keywords: keratoacanthoma; mohs micrographic surgery; non-follicular; palmar; trauma.

Figure 1. Palmar keratoacanthoma

Solitary, firm 1.5 x 1.2 cm crateriform nodule in the center of the left palm

Figure 2. Pathology features of keratoacanthoma

A well-defined nodular invasive squamous neoplasm with a cup-shaped invagination on the periphery. Well-differentiated neoplastic glassy squamous epithelioid cells arranged in a haphazard pattern surrounding multiple islands of keratin, consistent with keratoacanthoma, depicted in 40x (A) and 100x (B) magnification views