Fungi are microorganisms that are occasionally seen by pathologists.

Overview

There are lots of 'em. Below are a few of 'em.

Terminology:^[1]

Hyphae = microscopic filamentous growth (of fungi) -- single cell.
Mycelial = filamentous network of hyphae.
Septae/septation = hyphae may be subdivided by septae -- if they aren't they are one mass of protoplasm. (?)
Dimorphism = exist in two forms; e.g. single cell (yeast) and mycelial growth.
Pseudohyphae = looks like hyphae --but branching pattern is created by separate cells.^[2]

Tissue invasive fungi

Typically:^[3]

Mucor.
Aspergillus.

Summary table

Name (disease)	Kingdom	Size	Shape	Stains	Other (microscopic)	Clinical	References	Image
Aspergillus (aspergillosis)	Fungi	?	Hyphae that branching with 45 degrees angle	PAS-D	Fruiting heads when aerobic	? Immunosuppression	^[4]	Aspergillus (WC), Aspergillus cytology (WC)
Zygomycota (zygomycosis); more specific Mucorales (mucormycosis)	Fungi	?	Branching hyphae with variable width	?	Granulomata assoc.	Diabetes, immunodeficient	^[4]	Mucormycosis (homestead.com), Zygomycosis (WC)
Coccidioides, usually C. immitis (coccidioidomycosis)	Fungi	Large - 20-60 micrometers, endospores 1-5 micrometers	Spherules	Stains?	Other?	Immunodeficient	^[4]	Coccidioidomycosis (med.sc.edu) C. immitis (WC) (webpathology.com)
Histoplasma (histoplasmosis)	Fungi	2-5 micrometers	Spherical	GMS	Intracellular (unlike candida), granulomata	Source: soil with bird droppings	^[4]	Histoplasmosis (WC)
Blastomyces (Blastomycosis)	Fungi	5-15 micrometres	Spherical (yeast)	Stains?	Granulomas, broad-based budding yeast	Habitat: Northeast America, Africa	^[4]^[5]	Blastomyces
Paracoccidioides (Paracoccidioidomycosis)	Fungi	6-60 micrometres	Spherical (yeast)	Stains?	Multiple budding "steering wheel" appearance	Clinical???	^[4]	P. brasiliensis (WC).
Pneumocystis jirovecii (Pneumocystis carinii pneumonia; abbrev. PCP)	Fungi (previously thought to be a protozoan)	7-8 micrometres	"Dented ping-pong ball"	GMS	Usually in clusters of alveolar casts with a honeycomb appearance	HIV/AIDS associated	^[6]	PCP (WC)
Cryptococcosis	Fungi	5-15 micrometres	Yeast	GMS	Prominent (i.e. thick polysaccharide) capsule	HIV/AIDS associated, most common CNS fungus	^[4]	Crytococcosis - methenamine silver (WC), Crytococcosis - mucicarmine (WC).

Notes:

Bold text = key features.

Specific fungi

Histoplasmosis

Histoplasma capulatum - primative fungus, typical location: lung.
- Often in yeast form in tissue 2-5 micrometres.^[7]
- Nice bright red on PAS-D - histoplasmosis (wikipedia.org).
  - Have a "central dot"^[8] - histoplasma (ouhsc.edu).

Coccidiomycosis

Coccidioides immitis - fungus, from soil, typical locations: lung, oral cavity.^[9]
- Forms spherules 60-80 micrometres in size.^[7]
- Coccidioides (commons.wikimedia.org).

Pneumocystis pneumonia (PCP)

Pneumocystis jirovecii (used to be called Pneumocystis carinii) - fungus (that used to be considered a parasite), typical location: lung.
- Clinical: Opportunistic infection. May have subtle finding on chest x-ray.
- "Dented ping-pong ball" appearance;^[7] - remember PCP = ping-pong.
- Approximately 7-8 micrometres in size - PCP (WP). Several images are here (WC).

Cryptococcus

Usually C. neoformans, fungus - opportunistic infection, typical location: lung.
Most common fungus seen in CSF specimens.^[4]

Appearance:

Yeast:
- Round/ovoid 5-15 micrometres (may resemble Histoplasma or Candida -- but often larger).
- Thick mucopolysacchardie capsule + refractile centre.^[4]
- "Tear drop-shapped" budding pattern (useful to differentiate from Blastomyces, Histoplasma).^[4]

Images:

Notes:

May be confused with corpora amylacea in the CNS, esp. as they (like cryptococci) stain for methenamine silver, Alcian blue, and PAS.^[10]

Cryptosporidiosis

General

Caused by cryptosporidium.
Fecal-oral transmission.
Usu. in immunoincompetent individuals, e.g. HIV/AIDS.

Microscopic

Features:

Uniform spherical nodules 2-4 micrometres in diameter, typical location - GI tract brush border.
- Bluish staining of brush border key feature - low power.

Images:

Notes:

Cryptosporidium parvum?^[11]

Candidiasis

Commonly Candida albicans - yeast (fungus), locations: oral cavity, vagina.
Dimorphic - seen in two forms:
- Pseudohyphae^[9] - collections of many C. albicans cells in a branching pattern.
- Yeast form - single cells, 10 to 12 micrometres in diameter, gram positive.^[12]
Stains: PAS, methenamine silver.
Images:
- Candida (pseudohyphae) - methenamine silver (med.sc.edu).
- Candida on Pap test (WC).

Blastomycosis

Usually Blastomyces dermatitidis - fungus.
May be in the oral cavity.^[9]
Histology = Broad-based budding yeast -- is Blastomyces.^[13]
- The interface between two separating fungi, i.e. fungi in the process of reproducing, is very large.
Images:

Mucormycosis

General

Causative organism: Mucorales.
- Kingdom: Fungi.
- AKA Zygomycota (zygomycosis).
Assoc. with diabetes, immunodeficiency.

Microscopic

Features:^[4]

Branching hyphae variable width.
Granulomata associated.

Image:

References

↑ http://www.fungionline.org.uk/1intro/3growth_forms.html
↑ http://pathmicro.med.sc.edu/mycology/mycology-3.htm
↑ CM 17 Apr 2009.
↑ ^4.00 ^4.01 ^4.02 ^4.03 ^4.04 ^4.05 ^4.06 ^4.07 ^4.08 ^4.09 ^4.10 Lefkowitch, Jay H. (2006). Anatomic Pathology Board Review (1st ed.). Saunders. pp. 682. ISBN 978-1416025887.
↑ http://pathmicro.med.sc.edu/mycology/mycology-6.htm
↑ Lefkowitch, Jay H. (2006). Anatomic Pathology Board Review (1st ed.). Saunders. pp. 684. ISBN 978-1416025887.
↑ ^7.0 ^7.1 ^7.2 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 103. ISBN 978-0781765275.
↑ URL: http://moon.ouhsc.edu/kfung/jty1/opaq/PathQuiz/A6I001-PQ01-M.htm. Accessed on: 19 October 2010
↑ ^9.0 ^9.1 ^9.2 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 3. ISBN 978-0781765275.
↑ URL: http://flylib.com/books/en/2.953.1.17/1/. Accessed on: 15 December 2010.
↑ http://www.dpd.cdc.gov/dpdx/HTML/Cryptosporidiosis.htm
↑ http://pathmicro.med.sc.edu/mycology/mycology-3.htm
↑ PMID 12375640

[1] ttp://www.fungionline.org.uk/1intro/3growth_forms.html

[2] ttp://pathmicro.med.sc.edu/mycology/mycology-3.htm

[3] CM 17 Apr 2009.

[Ref_APBR682-4] 4.00 ^4.01 ^4.02 ^4.03 ^4.04 ^4.05 ^4.06 ^4.07 ^4.08 ^4.09 ^4.10 Lefkowitch, Jay H. (2006). Anatomic Pathology Board Review (1st ed.). Saunders. pp. 682. ISBN 978-1416025887.

[5] ttp://pathmicro.med.sc.edu/mycology/mycology-6.htm

[Ref_APBR684-6] Lefkowitch, Jay H. (2006). Anatomic Pathology Board Review (1st ed.). Saunders. pp. 684. ISBN 978-1416025887.

[Ref_WMSP103-7] 7.0 ^7.1 ^7.2 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 103. ISBN 978-0781765275.

[8] URL: http://moon.ouhsc.edu/kfung/jty1/opaq/PathQuiz/A6I001-PQ01-M.htm. Accessed on: 19 October 2010

[Ref_WMSP3-9] 9.0 ^9.1 ^9.2 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 3. ISBN 978-0781765275.

[10] URL: http://flylib.com/books/en/2.953.1.17/1/. Accessed on: 15 December 2010.

[11] ttp://www.dpd.cdc.gov/dpdx/HTML/Cryptosporidiosis.htm

[12] ttp://pathmicro.med.sc.edu/mycology/mycology-3.htm

[pmid12375640-13] PMID 12375640

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Fungi

Contents

Overview

Tissue invasive fungi

Summary table

Specific fungi

Histoplasmosis

Coccidiomycosis

Pneumocystis pneumonia (PCP)

Cryptococcus

Cryptosporidiosis

General

Microscopic

Candidiasis

Blastomycosis

Mucormycosis

General

Microscopic

See also

References

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