Pure neuritic leprosy with nerve abscess presenting as a cystic, soft tissue mass: report of a case diagnosed by fine needle aspiration cytology.

Pure neuritic leprosy (PNL) with nerve abscess manifesting as a huge, cystic, soft tissue mass is highly uncommon. Fine needle aspiration cytology can serve as an important initial diagnostic modality in such an instance. We report a case of 28-year-old male, who presented with a huge swelling in the lower, medial aspect of the right upper arm. The clinical diagnosis was schwannoma. Fine needle aspiration (FNA) yielded 80 ml of sticky, turbid, pale brown fluid. Cytologic examination revealed abundant, caseous, necrotic material and many degenerated neutrophils in a thin proteinaceous background. Stain for acid fast bacilli (AFB) was negative. Based on an AFB negative, caseous, necrotic material obtained from the soft tissue mass located in the ulnar nerve region, a cytodiagnosis of tuberculoid PNL with nerve abscess was given, and this was confirmed by the subsequent histopathologic examination. Our case emphasizes the major role of minimally traumatic, FNA technique in the diagnosis of rare cases of clinically unsuspected neuritic leprosies.