Utility of fine-needle aspiration cytology in the classification of leprosy

The role of fine-needle aspiration cytology (FNAC) in the diagnosis of benign skin lesions has been restricted primarily to the evaluation of bacteriologic and morphologic indices in leprosy. This study was undertaken to evaluate the efficacy of FNAC in the diagnosis and classification of lepromatous lesions. Aspirates of 94 newly diagnosed cases of leprosy were studied, and the bacterial load was determined by modified Ziehl-Neelsen (ZN) stain. A skin biopsy was taken from the same site at the same sitting. Frozen and paraffin sections stained with hematoxylin-eosin (H&E) and ZN stains were examined from the biopsy specimen. In 61 of 94 cases (64.9%), the aspirates were satisfactory. Both diagnosis and classification of leprosy were possible in 40 of these 61 cases; the rest of the aspirates showed nonspecific chronic inflammation. The 39 cases of leprosy where a biopsy was available from the same site were classified on FNAC into tuberculoid (TT and BT), lepromatous (LL and BL), and midborderline (BB) subtypes. Taking the histologic diagnosis and Ridley-Jopling classification to be the gold standard, a strong concordance in tuberculoid leprosy cases (18 of 20 cases, 90%) and in lepromatous cases (15 of 16 cases, 93.7%) was observed. Midborderline cases of leprosy posed a problem, and a correct cytohistological correlation was observed in only one of the three cases.