title: Differentiation of histoplasma and cryptococcus in cytology smears: a diagnostic dilemma in severely necrotic cases.
abstract: OBJECTIVE
  The correct identification of fungal organisms is important for the appropriate clinical management of patients. It becomes difficult in necrotic smears when the tissue response is not clearly discernible. It is difficult to distinguish between histoplasma and cryptococcus in severely necrotic cases, where both appear as variably sized clear refractile haloes.
  
  
  METHODS
  Four cases of adrenal necrotic histoplasma infection were studied and the morphology was compared with that of non-necrotic histoplasmosis and cases of cryptococcal infection. Eleven cases were analysed in fine needle aspiration cytology (FNAC) smears. Ziehl-Neelsen (ZN) stain was performed to exclude tuberculosis in necrotic smears. A clinical and serology correlation was performed where available.
  
  
  RESULTS
  Necrotic cases of histoplasma infection revealed negative refractile clear haloes similar to those of cryptococcus. Histoplasma showed methylene blue-stained organisms in ZN stains, whereas the cryptococcus cases were negative. Similar methylene blue-stained organisms were seen in non-necrotic histoplasma infection.
  
  
  CONCLUSIONS
  As a result of morphological overlap between cryptococcus and histoplasma, the distinction between the two fungi can be difficult in many cases. ZN staining appears to have a role in the differentiation of these fungi in severely necrotic cases. This observation needs to be validated on a larger number of cases with complete correlation with clinical, serology and treatment records.
authors.affiliation: Department of Pathology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: R
authors.initials: R
authors.lastname: Ranjan
authors.affiliation: Department of Pathology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: D
authors.initials: D
authors.lastname: Jain
authors.affiliation: Department of Pathology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: L
authors.initials: L
authors.lastname: Singh
authors.affiliation: Department of Pathology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: V K
authors.initials: VK
authors.lastname: Iyer
authors.affiliation: Department of Pathology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: M C
authors.initials: MC
authors.lastname: Sharma
authors.affiliation: Department of Pathology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: S R
authors.initials: SR
authors.lastname: Mathur
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D044963:Biopsy, Fine-Needle / Q000379:methods; D003453:Cryptococcosis / Q000175:diagnosis* / Q000382:microbiology* / Q000473:pathology; D003454:Cryptococcus / Q000472:pathogenicity; D003581:Cytodiagnosis / Q000379:methods; D005260:Female; D006658:Histoplasma / Q000472:pathogenicity; D006660:Histoplasmosis / Q000175:diagnosis* / Q000382:microbiology* / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged
keywords: Ziehl-Neelsen stain; cryptococcus; cytology; histoplasma; methylene blue; necrosis