Keratoacanthoma Centrifugum Marginatum with Spontaneous Regression and Its Possible Differential Diagnosis.

Keratoacanthoma centrifugum marignatum (KCM) is a rare variant of keratoacanthoma, which is characterized by the dense infiltration of inflammatory cells throughout the dermis, especially around the keratinocytic islands. Therefore, it is sometimes difficult to differentiate between KCM and cutaneous T-cell lymphomas. In this report, we describe a case of KCM with spontaneous regression that showed dense infiltration of CD3+CD8+ T cells. Our present case suggested the importance of investigating tumor-infiltrating lymphocytes to avoid the misdiagnosis of KCM as cutaneous T-cell lymphoma.