Australian Society of CytologyCase of the Month
September 2004 - Answer and Discussion
Cryptococcus neoformans.
Answer
Cytology
The smears contains remarkably abundant encapsulated Cryptococcus organisms with a minimal reactive response.(fig 1)
The background shows an unusual honeycomb-like pattern throughout the Diff Quik stained smears perhaps due to the gelatinous nature of the aspirated material. (fig 2)
At low power the fungal elements appear almost cellular, but higher magnification reveals the capsular nature and darker organism within the halo. (fig 3)
A cell block showed similar results. (fig 4) Organisms showed strong PAS positivity. (fig 5)
The cytology results were in agreement with the microbiology and yeast studies which identified the organisms as the Gattii variant of Cryptococcus neoformans.
Discussion
Cryptococcus neoformans is the organism found in soil and bird droppings which causes the disease Cryptococcosis.
Primary and opportunistic infection of individuals involving the lungs is common. However, infection may often provoke little or no inflammatory response. Dissemination to the central nervous system can occur in severe cases with the organism appearing in the CSF. (See ASC website April 2004 case of the month for such a case)
The organism measures 5-20µm in diameter. It has a thick mucoid capsule which stains bright pink with PAS stain. Macroscopically, an infected area of tissue will have a gelatinous surface due to this feature of the organism. Characteristic teardrop-shaped budding occurs in the reproduction of the organism.
Advanced infections can mimic the features of a lung tumour on x-ray imaging - note the “?Infective, ?Malignant” comment in the patient’s clinical notes. Thus FNA cytology is valuable in making a differential diagnosis.
References:
- Gray W,McKee G, Diagnostic Cytopathology, 2nd Edition,Churchill Livingstone 2003.
- Geisinger K,Raab S,Stanley M,Silverman J,Abati A, Modern Cytopathology, Churchill Livingstone 2004.
- Demay R, Practical principles of Cytopathology, ASCP Press 1999.
- Cibas E, Ducatman B, Cytology, Diagnostic principles and clinical correlates, 2nd Edition, Elsevier 1996.
