Opportunistic microsporidiosis unveiled by fine-needle aspiration cytology of cervical lymph node with literature review.

Microsporidia are highly specialized obligate intracellular organisms closely related to fungi, traditionally linked to diarrheal diseases in acquired immunodeficiency syndrome patients. Over the past two decades, an increasing incidence of extraintestinal infections affecting various organ systems, especially in immunocompromised individuals, has been observed. The report presents a unique case of lymph node microsporidiosis in a 38-year-old male, positive for human immunodeficiency virus, with coinfections of hepatitis B and C. Fine-needle aspiration cytology (FNAC) from cervical lymph node yielded pus-like, necrotic material with periodic acid-Schiff stained smear uncovering small round to oval spores on microscopy suspicious for microsporidia. Based on polymerase chain reaction and sequencing done with aspiration material, the causative agent was identified as Vittaforma corneae. This rare encounter highlights the significance of recognizing unique morphological characteristics of infectious organisms and employing appropriate ancillary techniques for precise identification. The case underscores the crucial role of FNAC in diagnosing opportunistic infections involving the lymph nodes and the growing significance of molecular tests for specific pathogen confirmation.