Pneumocystis jirovecii (carinii)
Epidemiology and
Etiology:
·
Symptomatic only in immunosuppressed
·
HIV
·
Steroid therapy
·
Hematopoietic neoplasms
Common sites:
·
lung
Gross features:
·
Histologic
features:
·
Prominent intra-alveolar accumulation of foamy material
·
Modest lymphocytic interstitial infiltrate
·
Diffuse alveolar damage maybe
·
Cyst stage (5-8um):
·
8 trophozoites (intracystic
bodies) develop within
·
Spherical to collapsed / helmet-shaped
·
Thickening of cyst wall produces a darker comma-shaped areas of
staining on GMS
·
Not stained by H&E or Giemsa
·
May be outlined as ghosts
·
Trophozoites (2-4um):
·
Granulomatous inflammation
uncommon
Immunophenotype:
|
Marker: |
Sensitivity: |
Specificity: |
|
GMS (cysts –
faint) |
||
|
Toluidine blue |
||
|
Giemsa (trophozoites) |
|
|
|
Diff-Quik (trophozoites) |
|
|
|
PAS (foamy
material) |
|
|
·
Note: faint staining
Molecular features:
·
Other features:
·
CMV may coinfect
References:
·
Silverberg SG, DeLellis RA, Frable WJ, LiVolsi VA, Wick MR.
Silverberg's Principles and Practice of Surgical Pathology and Cytopathology: 2-Volume Set. 4th ed. Churchill Livingstone;
2005:2656.