Fine needle aspiration cytology in leprosy

Background: Laboratory diagnosis of leprosy by slit skin smear and skin biopsy is simple but both techniques have their own limitations. Slit skin smear is negative in paucibacillary cases whereas skin biopsy is an invasive technique. Fine needle aspiration cytology (FNAC) from skin lesions in leprosy with subsequent staining with May-Grunwald-Giemsa (MGG) stain has been found useful.
Aim: To evaluate the possible role of cytology in classifying leprosy patients.
Methods: Seventy-five untreated cases of leprosy attending the outpatient department were evaluated. Smears were taken from their skin lesions and stained using the MGG technique. Skin biopsy was also done from the lesions, which was compared with cytology smears.
Results: A correlation of clinical features with FNAC was noticed in 87.5% of TT, 92.1% of BT, 81% of BL, and 66% of LL cases. Correlation of clinical with histopathological diagnoses revealed 12.5% specificity in TT leprosy, 55.3% in BT, 52.4% in BL and 50% in LL, and 100% in neuritic and histoid leprosy cases. Both correlations were found to be statistically significant by paired t test analysis. Thus, it was possible to distinguish the tuberculoid types by the presence of epithelioid cells and the lepromatous types by the presence of lymphocytes and foamy macrophages.
Conclusion: FNAC may be used to categorize the patients into paucibacillary and multibacillary types, but is not a very sensitive tool to classify the patients across the Ridley-Jopling spectrum.

Keywords
Fine needle aspiration cytology, Hansen′s disease, Leprosy, Mycobacterium leprae, Skin biopsy