Leprosy is a spectral disease. Its two polar forms, tuberculoid (TT) and lepromatous (LL), are distinct presentations of the disease, both from a clinical and histopathological/bacilloscopic point of view. In this chapter, the histopathological characteristics that define the two polar forms (TT and LL) are presented, and their main differential diagnoses are discussed. These two forms also have significant differences in their treatment protocol. Histopathological recognition of both forms of the disease is important for choosing the correct treatment. Also, there are a large number of diseases that can have a clinical presentation similar to the TT and LL forms of leprosy. In this context, histopathological examination is essential for defining the diagnosis of leprosy.
Keywords: Hansen's disease, Lepromatous leprosy (LL), Leprosy, Mycobacterium leprae, Tuberculoid leprosy (TT).