Fungal infections in histopathology

pathology histopathology exam md residency

1. Fungal infections
Dr. Manisha Tambekar

2. Fungal infection
•Fungal infections are called mycoses.
•Fungi are eukaryotes that grow by budding
( yeasts) or by filamentous extentions called
(molds)
•Candida albicans produce buds that fail to
detach become elongated, producing a chain
of elongated yeast cells called pseudohyphae.

3. Structure
•Main body: made up of fine, branching
colorless threads called hyphae.
•An individual fungal filament is called hypha.
•Several of these hyphae, all interwining to
make up a tangled web called the mycelium.

4. Morphological Classification
•Moulds : hyphae in form. Eg: ringworm or
dermatophytes.
•Yeasts : Single cell that bud to reproduce. Eg:
cryptococcus neoformans.
•Yeast like: Form Pseudohyphae. Eg: candida
albicans.
•Dimorphic fungi: have both a yeast form ( at
human body temp) and a mold form ( at
room temp ) eg: Blastomyces dermatitides.

5. Classification
•According to pathogenicity
1.Superficial mycoses
2.Mucocutaneous mycoses
3.Subcutaneous mycoses
4.Deep Mycoses / systemic.

6. Candidiasis
•Resides in the skin, mouth, GIT & vagina.
•Healthy people: live as benign commensals &
produce no disease.
•Candida albicans : frequent cause of human
fungal infections.
•Candida albicans grows on warm, moist surfaces
causing oral thrush, vaginitis & diaper rash.
•Diabetic & burn patients are prone to superficial
candida.

7. Candidiasis
•Directly introduced into the blood by IV lines,
catheters, peritoneal dialysis, cardiac surgery
or IV drug abuse.
•Disseminated candidiasis: Asso. with
neutropenia.
•Secondary to leukemia or anticancer therapy,
immunosupression after transplantation 7
neutrophil disorders.
•Causes shock & DIC.

8. Candidiasis
•Tissue sections: appears as yeastlike &
pseudohyphae.
•Pseudohyphae: imp diagnostic clue for C.
albicans & represent budding yeast cells
joined end to end at constrictions.
•Special stains : GMS ( gomori methenamine –
silver) & PAS ( periodic acid schiff)

9. Candidiasis
•Oral thrush: superficial infection on mucosal
surfaces of the oral cavity.
•Gray-white, dirty looking pseudomembranes
composed of matted organisms & inflammatory
debris.
•Mucosal hyperemia &inflammation.
•Commonly seen in newborns, debilitated pts.,
children receiving oral steroids for asthma &
following a course of antibiotics that destroy
competing normal bacterial flora & in HIV.

10. Oral thrush

11. Candida esophagitis
•Commonly seen in AIDS
patient & with
hematolymphoid
malignancy.
•Dysphagia, retrosternal
paining.
•Endoscopy: white
plaques &
pseudomembranes
resembling oral thrush.

12. Candidiasis

13. Candida esophagitis

14. Budding yeast

15. Candida vaginitis
•Common infection in diabetics or pregnant or
on oral contraceptive pills.
•Intense itching & a thick curd like discharge.
Chronic mucocutaneous candidiasis
•Chronic refractory disease afflicting mucous
membranes, skin, hair & nails.
•Asso. with underlying T-cell defect.

16. Cutaneous candidiasis
•Present in different forms
•Infection of nail proper :Onychomycosis
•Nail folds : Paronychia
•Hair follicles: folliculitis.
•Moist, intertriginous skin such as armpits or
webs of the fingers and toes : intertigo &
penile skin : Balanitis
•Diaper rash : seen in the perineum of infants ,
in the region of contact of wet diapers.

17. Invasive candidiasis
•Caused by blood- borne dissemination of
organisms to various tissues or organs.
•Common patterns :
1.Renal abscesses
2.Myocardial abscesses & endocarditis
( occurring in the setting of prosthetic valves
or in IV drug users).
3.Meningitis with parenchymal micro abscesses
4.Endopthalmitis

18. Invasive candidiasis
5. Hepatic abscesses
6. Candida pneumonia: B/L nodular infiltrates.
occurs in patient with acute leukemia's who are
neutropenic post-chemotherapy.

20. Cryptococcosis
•Cryptococcus neofarmans: encapsulated yeast
,causing meningoencephalitis in normal
individuals
•As opportunistic infection in pts. With AIDS,
leukemia, lymphoma, SLE, Hodgkin’s
lymphoma or sarcoidosis & in transplant
recipients.
•Present in soil & in bird (pigeon) droppings &
infects pts when it is inhaled.

21. Cryptococcosis
•It has yeast but not pseudohyphal or hyphal
forms.
•It has thick gelatinous capsule, valuable for
diagnosis.
•Capsular polysaccharites stains intense red
with PAS and mucicarmine in tissues and
detected with antibody-coated beads in an
agglutination assay.

22. Cryptococcosis
•India ink preparations create a negative
image, visualizing thick capsule as a clear halo
within a dark background, do not stain the
yeast.
•Lung – primary site of localization, mild
asymptomatic, forms solitary pulmonary
granuloma.
•CNS: Involving meninges, cortical gray matter
and basal nuclei.

23. Cryptococcosis
•In imunosuppressed gelatinous masses of fungi grow
in the meninges or expand perivascular Virchow-
Robin spaces within gray matter producing so-called
soap-bubble lesions.
•In non imunosuppressed patients or in those with
protracted disease fungi induce a chronic
granulomatous reaction composed of macrophages,
lymphocytes and FB type giant cells.
•In severely imunosuppressed: may disseminate
widely to skin, liver, spleen, adrenals and bones.

24. In lymphnode: mucicarmine stsain

25. India Ink

26. Aspergillosis
•It is a ubicutous mold that causes allergies
(brewer’s lung) and sinusitis, pneumonia and
fungemia in imunosuppressed patient.
•Factors that predispose to aspergillus
infectuon are neutropenia and
corticosteroids.
•They are transmitted by air-borne conidia, and
the lung is the major portal of entry.

27. Colonizing aspergillosis (aspergilloma)
•Implies growth of fungus in pulmonary cavities with
minimal or no invasion of the tissues.
•Cavities result from pre-existing tuberfungal
hypculosis, bronchitctasis, old infarcts, or abscesses.
•Prolifarating masses of fungal hyphae called fungal
balls form brownish masses lined free within cavities.
Chronic inflammation and fibrosis may also seen.

28. Invasive aspergillosis
•An opportunistic infection confined to
immunosuppressed and devilitated hosts.
•Priamry are seen in lung.
•Hematogenous dissemination involves heart
valves, brain and kidneys.
•Pulmonary lesions: necrotizing pneumonia
with sharply delineated, rounded, gray foci
with hemorrhagic borders referred to as
target lesions.

29. Invasive aspergillosis
•Aspergillus forms fruiting bodies and septate
filaments branching at acute angles(40
degree).
•They invade blood vessels.

30. Aspergillosis...

31. Aspergillosis : Grocott's methenamine silver GMS stained .

32. Zygomycosis (mucormycosis)
•Opportunistic infection caused by bread mold
fungi. These fungi are widely distributed in
nature and cause no harm to healthy
individuals.
•They infect immunosuppressed patients.
•Predisposing factors: neutropenia CS use, DM
and breakdown of cutaneous barrier (example
burns, surgical wounds, trauma).

33. Zygomycosis (mucormycosis)
•Transmitted by air-borne asexual spores.
•Inhaled spores produce infection in sinuses and
lungs.
•They form nonseptate, irregularly wide fungal
hyphae with frequent right-angle branching.
•Primary sites of invasion are nasal sinuses, lungs and
GIT.
•In diabetics fungus spread from sinus to the orbit
and brain giving rise to rhinocerebral mucormycosis.

34. Zygomycosis (mucormycosis)
•They cause local tissue necrosis, invade
arterial walls and penetrate periorbital tissues
and cranial vault.
•Meningoencephalitis follows, cerebral
infections and induced thrombosis.
•Lung: hemorrhagic pneumonia with vascular
thrombi and distil infarctions.

35. mucormycosis

36. mucormycosis

37. Histomorphological characteristic of
aspergillosis & mucormycosis
CharacteristicAspergillusMucormycosis
Width Narrow ( 3-6 µm) Wide (5-20 µm)
Caliber
Uniform Varying
Branching Regular ( acute angle)Random ( Right angle)
Branching orientationParallel/radial Random
Septum Common finding uncommon