The importance of the biopsy technique in the diagnosis of histoid leprosy.

Histoid leprosy (HL) was originally described by Wade in 1963 and is regarded as a rare variant of lepromatous leprosy (LL). These characteristic clinical lesions are firm, deeply adhered nodules with features reminiscent of dermatofibromas or keloids in a background of apparently healthy skin. The main histopathological findings described are the presence of spindle cell histiocytes immersed in a richly collagenized background, usually forming a nodular pattern of infiltration with sharply delimitation and positive staining for acid-fast bacilli. The classical form of HL lesions should be devoid of foam histiocytes and globi. However, we and other authors noticed that in most of the cases, despite characteristic clinical features, histopathology depicts a mixture of LL and HL patterns. Therefore, we present a case with clinical features similar to HL in which an excisional scalpel biopsy of a nodule demonstrated features of classical LL in the center of the lesion and features of HL in the periphery, highlighting that a proper biopsy technique could enhance the ability of the dermatopathologist to histopathologically diagnose cases of HL. In cases in which HL is clinically suspected, we advocate replacing the usual 4-mm incisional punch biopsy by a broader elliptical scalpel biopsy, encompassing the totality of the lesion whenever possible to achieve a reliable representation of the pathologic process.