Fungal Pathology in Tissue

Fungus in Tissue
Brief Review
Margie Morgan, PhD D(ABMM)

1. Fungus in Tissue Brief Review Margie Morgan, PhD D(ABMM) 1

2. Important Infections with Molds and Yeast Hyaline septate molds Yeast Aspergillus species Candida Pseudallescheria ( Scedosporium ) complex Cryptococcus Fusarium species Hyaline aseptate molds ( mucormycetes ) Dimorphic fungi Histoplasma capsulatum Coccidioides immitis and C. posadasii Blastomyces dermatitidis Sporothrix schenckii complex Penicillium ( Talaromyces ) marneffei Dematiacious molds Mycetoma Chromoblastomycosis Phaeohyphomycosis 2

3. Hyaline Septate Molds 3

4. Aspergillus Species in tissue Dichotomous = branching into two pieces Higher magnification 4

5. Aspergillus compared to Mucormycete fungi (Mucor ) Broad hyphae rare/no septations Broader hyphae than Aspergillus Branching more irregular/some at 90* angle Thinner hyphae than Mucormycete Regular septations , 45* angle branching referred to as dichotomous branching 5

6. Aspergillus and Pseudallescheria ( Scedosporium ) Aspergillus hyphae is usually broader than Scedosporium species Both show dichotomous branching, invade vessels, and have similar infections. 6

7. Aspergillus fumigatus Fungus ball Culture 30*C / 4 days Scotch Tape Prep A. fumigatus is the most common Aspergillus species to cause pulmonary or disseminated infection 7

8. Aspergillus fumigatus Aspergilloma formation in the lung fungus ball Invasion of blood vessels 8

9. Aspergillus niger Unusual to cause pulmonary infection, most often associated with ear infections 9

10. Aspergillus terreus Note: Intrinsic resistance to amphotericin Can disseminate and cause disease much like Aspergillus fumigatus 10

11. Aspergillus flavus Can cause infection much like Aspergillus fumigatus 11

12. Fusarium species Random branching of hyphae / no characteristic pattern Hyaline septate with banana shaped conidia 12

13. Mucormycetes – Mucor and Rhizopus Broad ribbon like hyphae without septations – can appear faintly staining Rhizopus Mucor 13

14. Dimorphic Molds 14

15. Blastomyces dermatitidis No color (negative) on Mucicarmine stain stain S lung lung Skin is a primary site of dissemination GMS PAS Dermis 15

16. Blastomyces dermatitidis Culture Scotch tape prep Growth 30* C In @ 2-3 weeks 16

17. Coccidioides immitis and C. posadasii Spherule formation in human tissue/ NO yeast forms Spherules 17

18. Coccidioides species Mold growth in 3-5 days at 30*C Alternating barreled arthroconidia Scotch tape preparation 18

19. Histoplasma capsulatum Bone marrow lung Yeast are usually intracellular within macrophages, 2-4 um in size 19

20. Histoplasma capsulatum In fixed tissue, P. brasiliensis forms multiple buds on the primary yeast cell, appears similar to macroconidia of Histoplasma H. capsulatum adhesive tape prep Tuberuculate macroconidia microconidia **Do not confuse Histoplasma mold phase with the yeast of Paracoccidioides brasiliensis complex in fixed tissue Growth in culture 30* C for 2 weeks Yeast of P. brasiliensis in fixed tissue 20

21. Sporothrix schenckii Dermis inflammation Yeast cells variable in shaper some Cigar shaped Asteroid body commonly the only structure observed Progression up lymphatics Adhesive tape preparation /spores form daisy head arrangement Culture at 30* C 21

22. Penicillium ( Talaromyces ) marneffei Skin – yeast like cells Bone marrow 30*C culture/ note red diffusible pigment surrounding green colony Adhesive prep of mold Skin lesions 22

23. Dematiacious (Black) Molds 23

24. Subcutaneous fungal infections Infection with dematiaceous (black) molds Chromoblastomycosis Phaeohyphomycoses Infection with dematiaceous (black) molds or higher bacteria (Nocardia) Mycetoma 24

25. Chromoblastomycosis Cauliflower (raised) skin lesions Naturally brown colored copper penny or sclerotic body identified in tissue 25

26. Phaeohyphomycosis GMS H & E stain Naturally brown colored hyphae in tissue Nodular skin lesions 26

27. Mycetoma Sulfur granule Actinomycotic Mycetoma Eumycotic Mycetoma Nocardia species Black ( dematiacious ) molds Sulfur granule formed in tissue Sulfur granule formed in tissue with thin filamentous bacteria with thick dark hyphae Swollen extremity 27

28. Candida species GI tissue C. Albicans pseudophyphae extensions growing out from colony 28

29. Cryptococcus species Yeast are round and variable in size (2-20um) with capsule. Capsule stains dark pink on mucicarmine stain 29