Lung - nontumor
Cryptococcus neoformans

Author: Elliot Weisenberg, M.D.(see Authors page)

Revised: 24 February 2017, last major update September 2011

Copyright: (c) 2003-2017,, Inc.

PubMed search: cryptococcus neoformans [title] pulmonary

Cite this page: Cryptococcus neoformans. website. Accessed December 14th, 2018.
Clinical features
  • Yeast, mostly encapsulated, found in pigeon droppings, that may cause mild infection after inhalation; usually confluent bronchopneumonia with "yeast lakes" of microorganisms and possibly coin lesions, but no evident host response (eMedicine)
  • May also cause meningitis
  • Latent infections can reactivate in immunosuppressed
  • CNS disease is a major concern in immunocompromised
  • Most commonly an opportunistic infection, but disease may occur in immunocompetent patients
  • Major virulence factor is capsular polysaccharide glucuronoxylomannin, which hinders phagocytosis by alveolar histiocytes and inflammatory cell recruitment and migration
  • Other virulence factors include melanin production (Fontana-Masson stain may be positive; melanin may have antioxidant properties) and enzymes that increase invasiveness
Case reports
Microscopic (histologic) description
  • Somewhat pleomorphic, round / oval yeast, 4 - 10 microns
  • Thick, mucinous capsule stains bright red with mucicarmine; some are unencapsulated
  • Narrow necked budding takes place
  • Smaller, unencapsulated forms resemble Histoplasma capsulatum
Microscopic (histologic) images

Images hosted on PathOut server:

Case of the Week #298:

Frozen section

Oil Immersion images


PAS stain

Images hosted on other servers:

Various images