The document discusses 5 case studies: 1. A duodenal biopsy showing Giardia lamblia infection 2. An ileal biopsy showing Entamoeba histolytica infection 3. A subcutaneous nodule biopsy showing cysticercosis 4. A splenic mass biopsy showing an Echinococcus granulosus (hydatid cyst) 5. A lung mass showing fungal infection suggestive of pulmonary cryptococcosis For each case, the summary provides key microscopic findings, impressions, and differentiating points about the infectious organisms observed. Differential diagnoses and descriptions of the pathogens are also discussed.

1. Slide Seminar
Dr. Om Jha
Pathology Resident
Shree Birendra Hospital; NAIHS

2. Case 1: Duodenum

3. Microscopic Findings

5. Summary:
• Section from duodenal biopsy shows four tissue bits
lined by simple columnar epithelium with goblet cells
exhibiting maintained crypts to villi ratio. No villi
blunting or increase in IEL noted. Numerous
eosinophilic pear shaped organism with paired nuclei is
noted in between the villi. Lamina propria shows
dense infiltration of chronic inflammatory cells
predominantly comprising plasma cells, lymphocytes
followed by eosinophils. Benign lymphoid follicles with
germinal center noted. Submucosa shows brunner
gland. No dysplasia or evidence of malignancy seen.
• Impression: Duodenal Biopsy;-Suggestive of protozoal
Infection; Giardiasis.

6. Giardiasis
Favouring points
• Numerous eosinophilic pear
shaped organism with
paired nuclei is noted inter
villious space,
• Dense lymphoplasmacytic
infiltrates and eosinophils
noted
Non-favouring points
• No increase in IEL
• No villious blunting

7. Introduction
• Protozoan infection associated with
malabsorption, chronic diarrhea.
• Spreads by fecally contaminated water,
common in underdeveloped countries.
• Affects 1/3 of homosexual men in urban
communities.

8. Introduction
• Attaches to mucosa but does not invade.
• May cause endoscopic duodenal nodularity.
• Causes epithelial barrier dysfunction by down
regulating claudin1 and increasing epithelial
apoptoses .

9. Introduction
• Clinical features -
usually two or more of
the following:
• Diarrhea - x5 days.
• Flatulence.
• Foul smelling feces.
• Nausea.
• Abdominal cramps.
• Excessive tiredness.
Etiology:
• Flagellate
protozoan Giardia
lamblia.
• Treatment
• Antibiotics, e.g.
metronidazole

11. Diagnosis
• Stool: Cysts,
trophozoites or
antigens.
• Positive stains:
– Trichrome with iron
hematoxylin
counterstain
– Giemsa stain
– KIT / CD117 may be
useful for diagnosis

12. THANK YOU

13. Case 2: Ileal biopsy, k/c/o crohn’s
disease

15. Summary
• Section from ileal biopsy shows four tissue bits lined by
simple columnar epithelium with goblet cells
exhibiting areas of ulceration. Crypt architectural
disruption is also noted. Underlying lamina propria
shows glands lined by simple columnar epithelium with
goblet cells along with chronic inflammatory cells
comprising of lymphocytes and few plasma cells.
Within the ulcer bed and exudates are numerous round
to oval shaped organisms are seen extending into the
submucosa. These organisms exhibit abundant
cytoplasm and small round nucleus and are showing
ingested erythrocytes. No dysplasia or evidence of
malignancy seen.
• Impression: Ileum, Biopsy:- Intestinal amebiasis (E.
histolytica)

16. E. histolytica:
Favouring points:
• Inflammatory exudates
• Chronic inflammatory cells
• Round to oval organisms
with abundant cytoplasm
with ingested RBCs.
Unfavouring points:
• Site: Ileum (uncommon site)

17. Differentials:
• Balantidium coli (Balantioides coli):
– Flask shaped ulcers resembling amebiasis
– Large (40 - 200 micrometers) ciliated trophozoites invading the
mucosa and submucosa
• Crohn's disease:
– Active chronic colitis
– No infiltrating trophozoites
• Histiocytes (also known as tissue macrophages):
– Present in various inflammatory and infectious conditions
– Similar size to Entamoeba histolytica trophozoites
– Large, often reniform nucleus (versus small round nucleus of E.
histolytica)
– CD68+

18. Entamoeba histolytica:
• A protozoan parasite
• Causes diarrhea, dysentry and liver abscess in
man
• Habitat: Trophozoites of E. histolytica live in
the mucous and submucous layers of the LI of
man
• Colon:
– Cecum is the most common site.
– Less common in ileum

19. • Transmission:
– ingestion of E. histolytica cysts in fecally contaminated
food or water (fecal - oral)
– sexual contact (oral - anal)
• Associated with:
– fever, abdominal pain, tenesmus, diarrhea (with or
without blood), dysentery
• May disseminate to the liver and other organs
• Flask shaped ulcers; rarely inflammatory mass
(ameboma), perforation

20. • Amebic trophozoites invade the submucosa
• Trophozoites with pseudopod projections, ingested
RBCs in cytoplasm, small round nucleus with dot-like
karyosome and peripheral rim of condensed
chromatin
• Trophozoites: CD68 negative, strongly PAS positive
• Treat:
– Metronidazole or Tinidazole: invasive dzs
– Paromomycin: eradicate luminal cysts

21. E. histolytica: Morphology
• Trophozoite
• Cyst
1. Cyst wall
2. Nucleus
3. Chromatoid bodies
4. Glycogen vacuole

22. Life cycle of E. histolytica
• Mainly 2 phases: Trophozoite and Cystic.
• Infective form: Mature quadrinucleate cyst.
• Transmission: Feco-oral route
Fig: Uninuclate, Binucleate and Mature
quadrinuclate cyst

24. Genesis of hepatic lesions
• Trophozoites are carried as emboli by the
radicles of the portal vein from base of ulcer.
• Capillary system of liver acts as filter and holds
the parasite
• Multiplication occurs
• Local accumulation  Obstruction 
Thrombosis of portal vein

26. Diagnosis:
• May be suspected based on:
– epidemiologic factors, patient symptoms, radiologic or colonoscopic
findings
• Detected via:
– stool microscopy (ova and parasite examination)
– stool antigen
– stool nucleic acid testing
• Serologic testing : antibodies supports the diagnosis of amebiasis
but cannot differentiate current from past infection
– Most useful for diagnosing disseminated disease
• Cyst aspiration:
– absence of other microorganisms supports evidence of amebic liver
abscess

27. THANK YOU

28. Case 3: Subcutaneous nodule

30. Summary
• Section from subcutaneous nodule shows tissue
composed of lobules of mature adipocytes
separated by thick fibromuscular septa. Within
these lobules lie a cystic cavity devoid of
epithelial lining but comprising of by fibroblasts,
multinucleated giant cells, ill-formed granulomas
and mixed inflammatory infiltrates. Cystic cavity
shows irregularly shaped double layered
eosinophilic membrane with numerous round to
oval spherical basophilic structure within.
Hemosiderin deposit in vacuolated spaces noted
in the membrane.
• Impression: Subcuatneous nodule:- Parasitic
infection suggestive of Cysticercosis

31. Cysticercosis:
Favouring points
• Irregularly shaped double
layered eosinophilic
membrane with numerous
round to oval spherical
basophilic structure
• Predominantly
multinucleated giant cells,
foreign body giant cells,
histocytes and epitheloid
cells.
Non favouring points
• No scolex and hooklet and
sucker noted.

32. Cysticercosis:
• Tissue infection caused by ingestion of larval cysts of the
cestode Taenia solium (cysticercus cellulose)
• Acquired by swallowing food, water or feces contaminated
by T. solium eggs
• In cystecicercosis, the human represents an intermediate
host and the parasite develops cysticerci in various organs
• Taeniasis: infection caused by the adult tapeworm in the
human intestine, which occurs from ingestion of larvae in
undercooked pork
• Cysticerci: larval forms of tapeworms found within a fluid
filled cyst

33. • Sites:
– Nervous system, heart,
skeletal muscle, eyes and
subcutaneous tissue
– Cases in breast are rare
• Etiology:
– Accidental ingestion of
eggs or gravid
proglottids of Taenia
solium by human host
via infected food, water
or feces
• Clinical features:
– Cysticercosis of the skin
is rare
• Palpable subcutaneous
nodule
– Breast: freely mobile
cystic mass
• Radiology description:
– CT scan: hyperdense
lesions in subcutaneous
tissue with or without
calcification
– USG: cystic lesions

34. • Diagnosis:
– History
– Skin biopsy
– Serology (serum or CSF)
– Imaging
• Positive stains
– Hooklets of cysticerci
can be acid fast
• Treatment:
– Praziquantel and
albendazole
– Large, solitary lesions:
Surgery
• Prolonged antiparasitic
therapy

36. Gross Examination
• Circumscribed, white to tan, cystic nodules containing a clear fluid
• Viable cysts are translucent, through which a single scolex may be
visible (2 - 3 mm nodule)
• As the cyst begins to degenerate, the fluid becomes dense and
opaque
• In the later stages, only a calcified nodule may be present
• Cyst sizes vary; commonly 1 mm - 2 cm
• Larval forms identified within the cyst cavity

38. Microscopic Findings:
• Cystic cavity contains the the larval form: scolex with hooklets and 2
pairs of suckers.
• The larval form, composed of duct-like invaginations, is lined by a
double layered, eosinophilic membrane.
• Scolex is single and invaginated; contains a rostellum, 4 suckers and
22 - 23 birefringent hooklets (may persist for a long time)
• Body wall exhibits a myxoid matrix and calcareous bodies (calcified
concretions)
• Cysticerci may remain viable for years

39. Microscopic Findings
Colloidal stage
• First stage of involution of
cysticerci
• Transparent vesicular fluid is
replaced by a turbid,
viscous fluid
• the scolex shows signs of
hyaline degeneration
Granular stage
• cysticercus is no longer
viable
• cyst wall thickens
• Scolex is transformed into
coarse mineralized granules

40. Microscopic Findings
• Host inflammatory reaction is usually not
present if the larva is viable.
• Finally, a granulomatous reaction develops
characterized by histiocytes, epitheloid cells
and foreign body giant cells,
• leading to fibrosis of the supporting stroma
and calcification of the parasitic debris

41. Microscopic Findings:

42. Microscopic Findings

43. Cytology: Findings
• Fibrillary stroma with interspersed nuclei and
a honeycomb pattern
• Parts of parasite may be identifiable
• Background usually consists of a mixed
inflammatory infiltrate
• Granulomas may be seen

45. Thank You

46. Case 4: Splenic mass

48. Summary:
• Section from splenic mass shows splenic
parenchyma composed of white pulp formed by
lymphatic nodules and the rest is composed of
vascular red pulp. There is a cystic cavity lined by
fibrous tissue with organisms inside that cavity.
The organism has outer acellular laminated
membrane, a germinal membrane and
protoscolices attached to the membrane. These
protoscolices are round to ovoid in shapes and
contain refractile sucker and hooklets.
• Impression: Splenic Biopsy:-Hydatid cyst (E.
granulosus)

49. Introduction
• Tissue invasive parasite
• Class: Cestoda
• Genus: Echinoccus
• Invade major tissues and organs of human
• Humans are accidental host(dead end host)
• Definitive host: Canines; Dog
• Intermediate host: Sheep

50. Adult form

52. Clinical features
• Commonly develop liver but may also involve
brain, lung, spleen, breast
• A liver cyst may produce no symptoms until it is
very large
• Pain and discomfort in upper abdominal region
• Nausea and vomiting with increasing size of cyst
or ruptured cyst
• Rupture of pulmonary cyst into bronchus can lead
to severe allergic reactions and coughing up of
blood mixed fluid containing hyadatid cyst tissue

53. Diagnosis
• Usually made on USG or CT scan
• Monoclonal antibodies to hydatid antigen
detection by immunoelectrophoresis, ELISA
and immunoblot

54. Case 5: Lung mass

56. Summary:
• Section shows two linear cores comprising of
fibrocollagenous tissue along with areas of
necrosis and hemorrhage. Numerous refractile
round to oval encapsulated organisms having thin
cell wall with budding are seen in
fibrocollagenous tissues as well as in necrotic
areas. Few foci also shows giant cells. Occasional
anthracotic pigments also noted. No atypical cells
or evidence of malignancy seen.
• Impression: Lung mass, Fungal infection
suggestive of Pulmonary cryptococcosis.

57. Favouring Points:
- Pulmonary mass.
- Round to oval encapsulated
yeasts having thin cell walls
with budding.
Non-favouring Points:

58. Differential Diagnosis:
• Unencapsulated strains mimic:
– Blastomyces and Candida species
– Fontana-Masson positivity is helpful
• Corpora amylacea in neural tissue:
– Concentric lamellations are helpful

59. Cryptococcosis:
• C. neoformans(immunocompromised), C. gattii
(immunocompetent).
• Size: 3-8μm in diameter.
• Disease ranges from cutaneous to severe pulmonary and CNS
disease.
• Pulmonary cryptococcosis: important opportunistic
invasive mycosis in immunocompromised patients
– also increasingly seen in immunocompetent patients.
• Main habitat: Debris around pigeon roosts and soil
contaminated with decaying pigeon or chicken droppings.

60. • Virulence factor: Antiphagocytic and poorly
immunogenic sugar capsule composed mainly
of GXM ( glucuronoxylomannan).
• Clinical features:
- Pulmonary disease: Cough , dyspnea, Pulmonary
nodules.
- CNS disease: Increased ICP, seizures, and focal
neurological deficits.
- Opportunistic infections.

62. Diagnosis
• Cryptococcal antigen (CrAg):
– Fast and sensitive test.
– Serum and cerebrospinal fluid
– Pulmonary dzs: sera rarely positive in the
absence of disseminated disease.
- Detects capsular polysachharide antigens

63. Laboratory
- Gram stain: Variably sized yeasts with
budding.
- India ink: Highlights organisms (Rarely used in
clinical practice)
- Culture: Sheep blood, chocolate agar and
fungal media. (Sabouraud dextrose agar).
- Rapidly grows within 24 hours at 37 degree
Celsius.
- Creamy , mucoid colonies formed.

64. Positive stains
Methenamine silver Mucicarmine

65. THANK
YOU