Role of S-100 immunocytochemistry in diagnosis of pure neuritic leprosy on fine needle aspiration cytology – A series of two interesting cases presented as nerve abscess

Pure neuritic leprosy (PNL) constitutes to 4.2 % of all leprosy cases in India. Histopathology is crucial for the diagnosis of PNL ,but fine needle aspiration cytology (FNAC) is now replacing it, as nerve biopsy is a cumbersome procedure and can lead to neurological deficits. FNAC, a minimally invasive procedure can play a significant role in primary diagnosis of PNL. Apart from the cytomorphological features , using ancillary tests can further improve the diagnostic accuracy of PNL. We present here two cases, who presented with a soft tissue swelling. FNAC attempted from the lesions yielded a necrotic material which on microscopy showed abundant caseous necrosis with epithelioid cell granulomas and there were also few spindle shaped cells of neural morphology seen in clusters as well as scattered in the necrotic background. S-100 immunostaing was attempted which highlighted the neuronal cells confirming the diagnosis of PNL.