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Gross and Microscopic Features
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(Left) Photo shows a skin
infection presenting as a firm,
ink nodule with central
hemorrhagic crust. Biopsy
showed involvement by
blastomycosis. (Right) Medium
magnification of a skin biopsy
on H&E stain shows numerous
yeast forms associated with
microabscesses. The yeast
size and presence of thick cell
wall put Blastomycosis on the
differentials, confirmed by
culture findings.
Fungal Infections: Morphological Diagnosis of Fungal Infections
(Left) Gross photo shows
cross section of a nasal mass
with pseudoepitheliomatous
hyperplasia on microscopic
examination. Culture confirms
resence of blastomycosis.
(Right) Low magnification
of a nasal mass on H&E
stain shows massive
seudoepitheliomatous
hyperplasia mimicking
squamous cell carcinoma.
Multifocal microabscesses
are noted. Presence of
Blastomyces sp. associated
with the microabscesses
was revealed by higher
magnification, follow-up GMS
stain, and culture findings.
BLASTOMYCOSIS
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(Left) Medium magnification o
a skin section shows crowding
big yeast forms with thick cell
wall highlighted by PAS stain.
Culture confirms the fungus to
be Blastomyces dermatitidis.
(Right) High magnification of
this tissue section on H&E stain
shows a yeast form
a neutrophilic abscess. The
size of the yeast form and the
appearance should warrant the
differential of blastomycosis.
within
Microscopic Features
Fungal Infections: Morphological Diagnosis of Fungal Infections
BLASTOMYCOSIS
(Left) High magnification of
a tissue section on GMS stain
shows medium to large yeast
forms with characteristic
broad-based budding
in a case of disseminated
blastomycosis. (Right) High
magnification of a tissue
section on H&E stain shows
a subtle fungal form
admixed with necrosis
and acute neutrophilic
inflammation in a patient
with history of disseminated
blastomycosis. Silver or PAS
stain would be helpful to
highlight the morphology of
the fungal organism.
(Left) Medium magnification
of a tissue section on GMS
stain shows 2 forms of
broad-based budding
exhibiting the initial stage of
division , and a division
that is almost complete .
The yeast size and type
of budding are consistent
with blastomycosis. (Right)
High magnification of a fineneedle aspiration of a splenic
lesion shows big yeast forms
with broad-based budding
and a thick cell wall, most
consistent with Blastomyces
spp.
(Left) High magnification
of a fine-needle aspiration
specimen on Diff-Quik stain
shows a large yeast form
with thick cell wall. No
budding is detected. The
findings raise the differential
of blastomycosis, which was
confirmed on subsequent
biopsy and culture. (Right)
High magnification of a fineneedle aspiration of a lesion
on ThinPrep shows big yeast
forms with thick cell wall
and broad-based budding
consistent with Blastomyces
spp.
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CANDIDIASIS
Section of esophageal mucosa shows abundant Candida
yeast forms and hyphal/pseudohyphal forms admixed
with bacteria.
Fungal Infections: Morphological Diagnosis of Fungal Infections
TERMINOLOGY
Synonyms
Candidosis
Definitions
Latin: "Candidatus" (a candidate for public office, who
dressed in white)
ETIOLOGY/PATHOGENESIS
Infectious Agents
Candida spp. are the most common cause of fungal
infections
> 20 different species reported as etiologic agents of
invasive candidiasis in humans
Candida albicans is the most common infectious agent,
accounting for 1/3-2/3 of invasive cases, followed by
Candida glabrata and Candida parapsilosis
Normal flora associated with skin, gastrointestinal and
genitourinary tracts of humans
Superficial infections
Minimal to suppurative inflammation
Occur when there are microbial imbalances caused
by fluctuations in reproductive hormones, antibiotic
use, and immunosuppression
Invasive infections
Various inflammatory responses depending on host
immune status
Primarily suppurative inflammation with rare
granulomas, invasion of blood vessels, necrotizing
vasculitis
Can involve any organ
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Umbilical cord PAS section demonstrates hyphal/
pseudohyphal forms and budding yeast forms consistent
with Candida in association with acute funisitis and
necrosis.
CLINICAL ISSUES
Epidemiology
Candida are ubiquitous organisms that cause disease
worldwide in a range of human hosts
Presentation
Superficial skin infections: Commonly seen in
immunosuppressed patients
Oropharyngeal candidiasis (thrush): White plaques
on buccal mucosa; commonly seen in patients with
immunodeficiency
Esophagitis: Most common in HIV-infected patients
and patients with hematologic malignancies
Vulvovaginitis: Most common form of mucosal
candidiasis
Mastitis: Lactating women with injured nipples are at
increased risk
Urinary tract infection
Renal infection: Often secondary to hematogenous
seeding in setting of disseminated candidiasis
Candiduria may represent merely colonization and
not infection; microscopic, culture, and clinical
correlation need to be made to determine its
relevance and need for antifungal therapy
Osteoarticular infections
Hematogenous seeding in cases of candidemia
Inoculation during trauma, intraarticular injection,
surgical procedures, or injection drug use
Meningitis
Manifestation of disseminated candidiasis, or
in premature neonates as a complication of
contaminated ventricular drainage devices
Endocarditis: Most common cause of fungal
endocarditis
Seen in intravenous drug users or patients with
prosthetic heart valves, indwelling central venous
catheters, or fungemia
Peritonitis and intraabdominal infections
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Etiology
Normal flora associated with skin, gastrointestinal
and genitourinary tracts of humans
Yeast form is associated with dissemination, and
hyphal form with adhesion and tissue invasion
Clinical Issues
Diseases range from superficial, invasive to
disseminated infections, depending on host immune
status
> 20 different species of Candida reported as etiologic
agents of invasive candidiasis in humans
Candida albicans is the most common agent for
invasive infections, followed by C. glabrata and C.
parapsilosis
CANDIDIASIS
Key Facts
Microscopic Pathology
Small yeast cells (2-6 m in diameter) intermingled
with pseudohyphae and branching septate hyphae
Suppurative inflammation and necrosis is often seen,
but inflammation can be minimal
Giant cells and granulomas are sparse
Ancillary Tests
Candida spp. are gram positive
Periodic acid-Schiff and fungal silver stains highlight
fungal forms for histologic examination
Top Differential Diagnoses
Aspergillosis
Trichosporon infections
Histoplasmosis
Cryptococcosis
Fungal Infections: Morphological Diagnosis of Fungal Infections
Often exists in polymicrobial infections that occur
following gastrointestinal tract perforation, or acute
necrotizing pancreatitis
Pneumonia: Rare
Empyema: Most commonly seen in patients with
malignancies
Pericarditis: Rare; often a complication of thoracic
surgery, contiguous spread from an adjacent focus, or
hematogenous spread
Endophthalmitis
Develops following trauma or eye surgery
Hematogenous seeding in cases of candidemia
Chronic disseminated candidiasis
Persistent microabscesses in liver, spleen, and
occasionally kidneys
Risk factors: Acute leukemia, neutropenia,
intravascular catheters
Chronic mucocutaneous candidiasis: Heterogeneous
group of syndromes with autoimmune manifestations
associated with chronic noninvasive Candida
infections of skin, nails, and mucous membranes
Laboratory Tests
Culture and Gram stain of biopsy tissue
Culture of blood or other body fluids
Non-culture methods
Biopsy for histopathologic examination
KOH preparation on skin scrapings to evaluate for
hyphae and pseudohyphae
-D-glucan in serum
Marker of fungemia or disseminated disease
Useful in patients with deep-seated invasive
candidiasis for which blood cultures may be
insensitive
Sensitivity: 57-90%; specificity: 44-92%
Treatment
Different species have slightly different intrinsic
susceptibilities to antifungal agents
Mucocutaneous infections
Therapy is dominated by azole antifungal agents
Invasive infections
Amphotericin Bbased preparations, azole and
echinocandin antifungal agents
Prognosis
Successful treatment depends on site of lesion and
immune status of host
MICROBIOLOGY
Fungal Features
In tissue and cytologic preparations
Round to oval yeast cells (2-6 m in diameter); size
varies according to species
Pseudohyphae and branching septate hyphae
C. glabrata only forms small (2-4 m in diameter)
oval yeast cells; no pseudohyphae are formed
Culture
Species identified according to macroscopic colony
morphology on agar and microscopic morphology on
specific medium
Microscopic morphology on cornmeal-Tween 80 agar
Pseudohyphae and some true hyphae with clusters
of round blastoconidia (blastospores) at septa
Terminal chlamydospores are formed
Most are rapid growers that mature in 3-5 days
MICROSCOPIC PATHOLOGY
Histologic Features
Small yeast cells (2-6 m in diameter) intermingled
with pseudohyphae and branching septate hyphae
Neutrophilic inflammation with some lymphocytes
and macrophages, fibrin, and coagulative necrosis
Giant cells and granulomas can be present but are
sparse
Mycotic aneurysms or thrombophlebitis can occur in
cases of vascular invasions
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CANDIDIASIS
A
Superficial mucosal infections can be associated with
enlarged hyperchromatic nuclei with perinuclear halos
in gynecologic specimens or pap smears
Changes can be confused with low-grade squamous
intraepithelial lesions
ANCILLARY TESTS
Histochemistry
Gram stain: Candida spp. stain purple/blue (gram
positive)
Fungal silver stains (Gomori methenamine silver
(GMS): Fungal cell wall appears black or dark brown
Periodic acid-Schiff (PAS): Fungal cell wall appears pink
to red-purple
In Situ Hybridization
Peptide nucleic acid fluorescent in situ hybridization
can identify the most frequent Candida spp. directly
from positive blood culture bottles without need for
subcultures
Fungal Infections: Morphological Diagnosis of Fungal Infections
Probes used to detect fungi are unique, organismspecific rRNA targets
PCR
Direct PCR using blood samples
Better sensitivity and specificity for diagnosis of
invasive candidiasis than blood cultures
Its effects on clinical outcomes are still being
investigated
DIFFERENTIAL DIAGNOSIS
spergillosis
Nonpigmented (hyaline), uniform, septate hyphae
with dichotomous branching at 45 angles
Aspergillus hyphae may be mistaken for nonbudding
yeast cells when the hyphae are cut transversely on
sections
Candida spp. form pseudohyphae with distinct
constrictions in addition to true hyphae
Fungal hyphae of Aspergillus spp. may be scant or
fragmented on histologic or cytologic preparations,
making it challenging to assess for septation and type
of branching
Trichosporon Infections
Pleomorphic yeast-like cells (3-8 m in diameter)
intermingled with pseudohyphae, septate true hyphae
without predominant dichotomous branching
Distinguished by the presence of arthroconidia
(formed by fragmentation of true hyphae), which can
be sparse or absent on tissue sections
Candida spp. lack pseudocapsule and stain better with
H&E and Gram stain
Candida spp. generally tend to generate suppurative
tissue reaction, while it is more common among
Histoplasma spp. to elicit a granulomatous reaction
Cryptococcosis
Narrow-based budding pleomorphic yeast forms (4-10
m in diameter)
Fontana-Masson stain is positive in melaninproducing Cryptococcus and mucicarmine stain
highlights capsule of Cryptococcus spp.
DIAGNOSTIC CHECKLIST
Clinically Relevant Pathologic Features
Generally elicits an acute suppurative inflammation
Coagulative necrosis often seen in neutropenic
patients
Granulomas rarely occur; mostly seen in chronic
systemic candidiasis
Pathologic Interpretation Pearls
Small round to oval budding yeast cells,
pseudohyphae, and branching septate true hyphae
Candida spp. are gram positive
SELECTED REFERENCES
1. Guarner J et al: Histopathologic diagnosis of fungal
infections in the 21st century. Clin Microbiol Rev.
24(2):247-80, 2011
2. Lyon GM et al: Antifungal susceptibility testing of Candida
isolates from the Candida surveillance study. J Clin
Microbiol. 48(4):1270-5, 2010
3. Concia E et al: Epidemiology, incidence and risk factors for
invasive candidiasis in high-risk patients. Drugs. 69 Suppl
1:5-14, 2009
4. Moriarty AT et al: Performance of Candida-fungal-induced
atypia and proficiency testing: observations from the
College of American Pathologists proficiency testing
program. Arch Pathol Lab Med. 133(8):1272-5, 2009
5. Pappas PG et al: Clinical practice guidelines for the
management of candidiasis: 2009 update by the Infectious
Diseases Society of America. Clin Infect Dis. 48(5):503-35,
2009
6. Wilson DA et al: Multicenter evaluation of a Candida
albicans peptide nucleic acid fluorescent in situ
hybridization probe for characterization of yeast isolates
from blood cultures. J Clin Microbiol. 43(6):2909-12, 2005
7. Kontoyiannis DP et al: Hepatosplenic candidiasis. A
manifestation of chronic disseminated candidiasis. Infect
Dis Clin North Am. 14(3):721-39, 2000
8. Herrod HG: Chronic mucocutaneous candidiasis in
childhood and complications of non-Candida infection:
a report of the Pediatric Immunodeficiency Collaborative
Study Group. J Pediatr. 116(3):377-82, 1990
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Histoplasmosis
Small yeast forms (2-4 m in diameter) with narrowbased budding
Often intracellular in macrophages but extracellular
Histoplasma spp. can be easily confused with yeast
forms of Candida spp., particularly C. glabrata, which
lacks pseudohyphae production
Gross and Microscopic Features
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Fungal Infections: Morphological Diagnosis of Fungal Infections
CANDIDIASIS
(Left) Liver section from
a patient who died of
disseminated multiorgan
fungal disease shows
multiple nodular abscesses
, which are PCR-
confirmed to be caused by
Candida albicans. (Right)
Fungal hyphal/pseudohyphal
forms consistent with
Candida are present in
ectocervix with acute and
chronic inflammation.
(Left) PAS stain highlights
rare hyphal/pseudohyphal
forms and yeast forms
consistent with Candida
in vulvar epithelium .
Minimal inflammation
is present. (Right) Skin
section with central
necrosis and hemorrhage
shows abundant Candida
organisms secondary to
hematogenous spread of
systemic infection. In areas
of extensive necrosis, hyphal
seudohyphal forms may
assume a more swollen and
distorted appearance.
(Left) GMS stain of
esophageal mucosa shows
numerous yeast forms,
seudohyphae, and true
hyphae with septa consistent
with Candida. Germinating
Candida blastospores
can appear to be branching.
(Right) Gram-stained
section of gastric pylorus
shows multiple yeast forms
and hyphae positive for
Gram stain, consistent with
Candida spp.
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CHROMOBLASTOMYCOSIS
High magnification of a skin section on H&E stain shows
thick-walled, brown sclerotic bodies in association
with microabscess and a multinucleated giant cell ,
consistent with chromoblastomycosis.
Fungal Infections: Morphological Diagnosis of Fungal Infections
TERMINOLOGY
Definitions
Greek: "khroma" (color) + "blastos" (sprout, germ) +
"mykes" (fungus, mushroom)
ETIOLOGY/PATHOGENESIS
Infectious Agents
Black yeast or dematiaceous fungi: Infectious species
produce dematiaceous mycelium
Common agents
Fonsecaea pedrosoi: Most common agent;
less sensitive to antifungal therapy than
Cladophialophora carrionii or Pocillopora verrucosa
C. carrionii
Phialophora verrucosa
Less common agents
Fonsecaea compacta
Rhinocladiella aquaspersa
Exophiala dermatitidis
Exophiala jeanselmei complex
Fungi causing chromoblastomycosis are present
in environment as part of the microbiota, which
decompose organic matter in soil and water
Fungi cause skin and subcutaneous infection via
direct inoculation of fungi through contact with
contaminated soil, plants, or rotting wood
CLINICAL ISSUES
Epidemiology
Occurs worldwide but most cases are found in tropical
and subtropical areas of Americas, Asia, and Africa
Species causing chromoblastomycosis vary by region
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and climate
e.g., F. pedrosoi is associated with humid areas with
a tropical and subtropical climate, and causes most
Medium-power H&E stain of a skin section shows brown,
thick-walled fungal forms in a granuloma in a patient
with known chromoblastomycosis. Small neutrophilic
foci are present.
cases in Brazil, Mexico, northern Madagascar, and
Japan
e.g., C. carrionii is associated with a semi-arid
climate, and causes most cases in Australia, southern
Madagascar, South Africa, and Cuba
In tropical and subtropical countries, infection more
commonly affects male agricultural workers in rural
regions, possibly due to increased chance of injury
with parts of plants affected by fungi responsible for
chromoblastomycosis
Presentation
Fungi gain entry into human body through cutaneous
wounds and can affect virtually any skin site
Most common sites of infection are distal limbs,
especially feet
Skin lesions on other sites have also been reported,
e.g., cornea, face, trunk
Primary lesion can enlarge and develop into various
forms and sizes
Nodular type
Small pale pink or purple nodules, which may
gradually grow into bigger tumoral lesions
Tumoral type
Papillomatous, tumor-like masses with
cauliflower-like appearance; most common on feet
and lower parts of shin
Verrucous type
Resembles verruca vulgaris (common warts);
frequently seen along edges of feet
Raises differentials of verrucous variants of
leishmaniasis and tuberculosis, sporotrichosis, and
verrucous carcinoma
Cicatricial type
Annular lesions that extend radially, leaving
central areas of scarring
Plaque type
Planoconvex lesions of various shapes and sizes
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CHROMOBLASTOMYCOSIS
Etiology
Most common agents: Fonsecaea pedrosoi,
Cladophialophora carrionii, Phialophora verrucosa
Agents are dematiaceous fungi
Cause skin and subcutaneous infections via direct
fungal inoculation
Clinical Issues
Occurs worldwide, but most cases are reported in
tropical and subtropical areas of Americas, Asia, and
Africa
Most common sites of infection: Distal limbs
Infection mostly confined to skin and subcutaneous
fat and does not invade into underlying muscle or
bone
Low cure rates and high relapse rates, especially in
chronic and extensive disease
Infection mostly confined to skin and subcutaneous
fat and does not invade into underlying muscle or
bone
Disease dissemination in form of satellite lesions may
occur via scratching autoinoculation, resulting in
fungal spread by lymphatic system
Complications
Secondary bacterial infections and ulcerations are
common
Lymphedema and elephantiasis in severe cases have
been reported
Development of squamous cell carcinoma has been
reported in association with chromoblastomycosis
in case studies
Rare reports of invasive infections to other organs
such as lung and brain had been made
Controversy exists, as some of those cases were
believed to be phaeohyphomycosis instead of
chromoblastomycosis
Laboratory Tests
Serological tests
Serological tests have been developed to detect
chromoblastomycosis caused by F. pedrosoi and C.
carrionii
Sensitivities of these assays range from 78-100%,
and specificities range from 83-99%
Not routinely or widely used in diagnosis
Treatment
Treatment choice and outcome depend on etiological
agent, clinical presentation, and presence of
complications
Common antifungal drugs for treatment: Itraconazole,
terbinafine, posaconazole, 5-fluorocytosine
Antifungal drugs have also been used in conjunction
with other methods such as cryosurgery and
thermotherapy to eradicate skin lesions
Combination of laser vaporization and
thermotherapy has been reported to eradicate
lesions successfully in patients with relapses
Key Facts
Macroscopic Pathology
Characteristic "black dots" can form in skin lesion
due to migration of fungi to skin surface and keratin
scales
Microscopic Pathology
Brown, thick-walled Medlar bodies (5-12 m in
diameter) with horizontal &/or vertical septations
Branched septate hyphae (3-5 m in diameter)
Fungi multiply by septation (binary fission) rather
than budding
Associated with granulomatous inflammation,
accompanied by suppurative reaction and
pseudoepitheliomatous hyperplasia
Top Differential Diagnoses
Phaeohyphomycosis
Prognosis
Low cure rates and high relapse rates, especially in
chronic and extensive disease
Mortality: Rare
MICROBIOLOGY
Culture
Routine fungal cultures (Sabouraud dextrose agar)
Allows species identification
Yield from tissue can be low
Fungal species are slow growing and require > 2 weeks
to mature
MACROSCOPIC FEATURES
General Features
Characteristic "black dots" can form in skin lesion due
to migration of fungi to skin surface and keratin scales
MICROSCOPIC PATHOLOGY
Histologic Features
Brown-pigmented fungi
Characteristic Medlar bodies/muriform cells/"copper
pennies"
Fungi multiply by septation (binary fission) rather
than budding
Branched septate hyphae (3-5 m in diameter) may
also be seen
Features of tissue reaction
Round to polyhedral thick-walled sclerotic bodies
(5-12 m in diameter) with horizontal &/or vertical
septations
Pseudoepitheliomatous hyperplasia, hyperkeratosis,
parakeratosis
Associated with granulomatous inflammation
Neutrophilic inflammation and microabscesses may
also be present
Fungal Infections: Morphological Diagnosis of Fungal Infections
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CHROMOBLASTOMYCOSIS
ANCILLARY TESTS
Histochemistry
Fungal organisms are positive for Gomori
methenamine silver (GMS) and periodic acid-Schiff
(PAS) stains
Direct Examination of Clinical Specimens
Skin scrapings from lesion can be treated with 10%
potassium hydroxide for direct microscopy
Diagnosis is made when brown Medlar bodies are seen
Molecular Diagnostics
PCR-based assays targeting ribosomal DNA for
Fonsecaea spp. and C. carrionii have been developed
Not widely available in endemic areas
DIFFERENTIAL DIAGNOSIS
Phaeohyphomycosis
Skin and/or subcutaneous infection caused by brown-
Fungal Infections: Morphological Diagnosis of Fungal Infections
pigmented fungi producing hyphal forms in tissue
Fontana-Masson stains cell walls of agents of both
phaeohyphomycosis and chromoblastomycosis
Common genera: Bipolaris, Cladophialophora,
Coniothyrium, Curvularia, Exophiala, Exserohilum,
Lasiodiplodia, Phialophora, Ochroconis, and Wangiella
In contrast to fungal species causing
chromoblastomycosis, Medlar bodies are absent in
phaeohyphomycosis, which often presents with yeastlike cells as well as brown-pigmented hyphae with
constricted septations and large vesicular swellings
In phaeohyphomycosis, an encapsulated cystic
granulomatous reaction associated with suppurative
exudate is often present in dermis and subcutaneous
tissue; epidermis is often spared
Blastomycosis
Distinguished by lack of pigmentation in yeast forms
Coccidioidomycosis
Distinguished by lack of pigmentation in yeast forms
and may have large spherules with endospores
Hemosiderosis
Excessive iron in macrophages may produce round to
oval collections mimicking pigmented yeast
Pathologic Interpretation Pearls
Characteristic brown thick-walled Medlar bodies
(5-12 m in diameter) with horizontal &/or vertical
septations
Branched septate hyphae (3-5 m in diameter) may
also be seen
Associated with granulomatous inflammation as well
as pseudoepitheliomatous hyperplasia
SELECTED REFERENCES
1. Queiroz-Telles F et al: Challenges in the therapy of
chromoblastomycosis. Mycopathologia. 175(5-6):477-88,
2013
2. Jamil A et al: Invasive squamous cell carcinoma arising
from chromoblastomycosis. Med Mycol. 50(1):99-102,
2012
3. Torres E et al: Chromoblastomycosis associated with
a lethal squamous cell carcinoma. An Bras Dermatol.
85(2):267-70, 2010
4. Ameen M: Chromoblastomycosis: clinical presentation and
management. Clin Exp Dermatol. 34(8):849-54, 2009
5. de Andrade TS et al: Rapid identification of Fonsecaea by
duplex polymerase chain reaction in isolates from patients
with chromoblastomycosis. Diagn Microbiol Infect Dis.
57(3):267-72, 2007
6.
Lpez Martnez R et al: Chromoblastomycosis. Clin
Dermatol. 25(2):188-94, 2007
7.
Oberto-Perdign L et al: [An ELISA test for the study of
the therapeutic evolution of chromoblastomycosis by
Cladophialophora carrionii in the endemic area of Falcon
State, Venezuela.] Rev Iberoam Micol. 22(1):39-43, 2005
8. Abliz P et al: Specific oligonucleotide primers for
identification of Cladophialophora carrionii, a causative
agent of chromoblastomycosis. J Clin Microbiol.
42(1):404-7, 2004
9. Bonifaz A et al: Treating chromoblastomycosis with
systemic antifungals. Expert Opin Pharmacother.
5(2):247-54, 2004
10. Vidal MS et al: Highly specific and sensitive, immunoblotdetected 54 kDa antigen from Fonsecaea pedrosoi. Med
Mycol. 42(6):511-5, 2004
11. Vidal MS et al: Immunoprecipitation techniques and Elisa
in the detection of anti-Fonsecaea pedrosoi antibodies
in chromoblastomycosis. Rev Inst Med Trop Sao Paulo.
45(6):315-8, 2003
12. Rubin HA et al: Evidence for percutaneous inoculation as
the mode of transmission for chromoblastomycosis. J Am
Acad Dermatol. 25(5 Pt 2):951-4, 1991
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Foreign Body
Fragments of wood or plant matter may have pigment
and morphology suggestive of yeast and produce
similar lesions after traumatic introduction
DIAGNOSTIC CHECKLIST
Clinically Relevant Pathologic Features
To confirm diagnosis, presence of muriform/Medlar
bodies and identification of an etiological agent in
culture are necessary
Relapse of disease is common
Microscopic Features
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Fungal Infections: Morphological Diagnosis of Fungal Infections
CHROMOBLASTOMYCOSIS
(Left) Low magnification
of a skin section on
H&E stain shows
seudoepitheliomatous
hyperplasia and focal
ranulomatous reaction
in a patient with known
chromoblastomycosis.
(Right) High magnification
of this skin section on H&E
stain shows multifocal
microabscesses in the
epidermis and dermis. A
small cluster of brown-
igmented fungi is
resent. The findings put
chromoblastomycosis on the
top differentials.
(Left) High magnification
of this skin section on
PAS stain highlights a
characteristic thick-walled
sclerotic body with
septation in a patient with
chromoblastomycosis.
The other fungal form
may represent a short
segment of septate hyphae
or daughter cells that are
undergoing binary fission.
(Right) High magnification
of this skin section on GMS
stain shows thick-walled
sclerotic bodies with
septations, consistent with
chromoblastomycosis.
(Left) Medium magnification
of this biopsy on H&E
stain shows necrotizing
ranulomatous inflammation
with large round pigmented
fungal forms , which
may represent an agent
of chromoblastomycosis
or phaeohyphomycosis.
Correlation with culture is
needed for diagnosis. (Right)
High magnification of this
tissue section on H&E stain
shows large, pigmented,
yeast-like cells and septate
hyphae. Culture is needed
to differentiate between
haeohyphomycosis or
chromoblastomycosis.
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