The different clinical forms through which leprosy manifests are called spectrum of the disease that goes from indterminate (I), to tuberculoid (TT), borderline tuberculoid (BT), borderline (BB), borderline lepromatous (BL) and lepromatous (LL).

Each of these forms is accompanied by specific histopathological picture. Thus towards TT end of the spectrum, histopathology shows epitheloid cells, langhans giant cells and lymphocytes, while towards LL end of the spectrum, there are more foamy macrophages, foreign body giant cells and band of Unna.