A case series of dermatofibromas originating in leprosy lesions: a potentially misdiagnosed condition

Leprosy is a chronic and slowly progressive disease caused by Mycobacterium leprae that particularly affects the skin and peripheral nerves. Its clinical spectrum usually correlates directly with histological findings, reflecting the different grades of the host cell-mediated immune response against the bacilli (Massone et al. 2015; Cruz et al. 2017).

Particularly in hyperendemic regions, the appearance of nodular lesions within regressive leprosy lesions (RLL) may be clinically challenging (Massone et al. 2015). To distinguish among relapses, reinfections, histoid leprosy, keloidal reactions, immunologic reactions or even common cutaneous nodules, clinicians and pathologists should be aware of some important clinical-histological correlations. Furthermore, histological details may be useful, directly influencing important choices among strikingly different therapeutic options (Massone et al. 2015; Nath et al. 2015; Talhari et al. 2015).

Dermatofibroma (DF) is a common mesenchymal cutaneous lesion, also known as superficial benign fibrous histiocytoma (Yamamoto 2009; Han et al. 2011). Most cases are relatively easy to diagnose clinically. However, DFs are not usually thought to be the first differential diagnosis when facing lesions in a leprosy patient, even in those with RLL.

This study aimed to describe the clinical and histological patterns of a series of cases of DFs diagnosed in leprosy patients compared to those diagnosed in patients without leprosy and to discuss possible mechanisms and implications of these findings, as well as to review the most common differential diagnoses of lesions forming inside RLL.