Tuberculous lymphadenitis: extended cytomorphologic features.

In tuberculous lymphadenitis, FNAC smears sometimes reveal only caseous necrosis without epithelioid cell granuloma. They pose a diagnostic problem, if AFB staining is negative. The diagnostic clue noticed in these cases was presence of multiple pink, homogenous structures with irregular shape and well-defined margins: "eosinophilic structures" (ES). The purpose of the present study is to find out the nature of ES and their role in the diagnosis of tuberculosis. Seventy FNAC smears from documented cases of tuberculous lymphadenitis were classified according to their cytomorphological features. The association and relation of ES with other morphological criteria was noted. Immunoperoxidase staining was performed to find out the reactivity of ES to tuberculous antigen. Its intensity of positivity was compared with epithelioid cell granuloma and degenerating granuloma. It was concluded that ES are degenerated granuloma and thus form an extended diagnostic criterion.