Correlation of eosinophilic structures with detection of acid-fast bacilli in fine needle aspiration smears from tuberculous lymph nodes: Is eosinophilic structure the missing link in spectrum of tuberculous lesion?

BACKGROUND: Acid-fast bacilli (AFB) is not seen in all necrotic tuberculous lesions. If the subset of tuberculous lesions which yield positive result for AFB can be identified, it would save on time and manpower besides optimizing use of resources. A prospective study was undertaken to assess if presence of eosinophilic structures (ESs) in necrotic tuberculous lesions correlated with the presence of AFB. MATERIALS AND METHODS: Patients referred for fine needle aspiration cytology for evaluation of lymphadenopathy between July 2012 and June 2013 were analyzed. The hematoxylin and eosin and May-Grünwald-Giemsa stained slides were screened for epithelioid cell granuloma, ES and necrosis and Ziehl Neelsen stained smears for AFB. RESULT: One hundred and eight tuberculous lymph nodes yielded necrotic material on aspiration. Four cytologic pictures were seen: (a) ES(+) AFB(+) in 58.33%, (b) ES(+) AFB(−) in 20.37%, (c) ES(−) AFB(+) in 9.26% (d) ES(−) AFB(−) in 12.04% cases. Overall AFB was found in 67.59% cases, out of which 58.33% correlated with the presence of ES while 9.26% were seen in smears without ES. CONCLUSION: Presence of ESs should be included in the morphological description of tuberculous lesions. In the absence of granulomas, they indicate tuberculous nature of the lesion. Presence of ES mandates a search for AFB as probability of finding AFB is high in such lesions. Significance of ES lies in their presence and not in their absence. Eosinophilic structures appear to be the missing link in the spectrum of tuberculous lesion.