Periapical Granuloma

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Periapical Granuloma
-Granulation tissue (fibrovascular) -Mononuclear
inflammatory cell infiltrate -chronic
inflammation
Chronic inflammatory reaction in response to a
pulpal infection with bacteria. All we can see
here are tiny blue dots sprinkled across the
entire tissue section. As we shall see next,
These are blood leukocytes that have migrated out
of vessels into tissue to form what is known as
an inflammatory cell infiltrate.
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Periapical Granuloma
-Granulation tissue (fibrovascular) -Mononuclear
inflammatory cell infiltrate -chronic
inflammation
Here we can see some small vessels (arrow) and
only faint, immature collagen in the background
(pink). The dots sprinkled all around are
leukocytes at this magnification, we cant
definitively identify what types of whites cells
they are.
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Periapical Granuloma
-Granulation tissue (fibrovascular) -Mononuclear
inflammatory cell infiltrate -chronic
inflammation
The red arrows point to small round blue nuclei
and represent lymphocytes. The blue arrows
designate plasma cells you can see an eccentric
nucleous with a purple cytoplasm. Elsewhere in
this view, capillaries are present, eosinophilic
(pink) collagen is in the background and some of
the more spindle shaped cells are fibroblasts.
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PA Gran, Subacute Inflammation
Notice that the inflammatory cell infiltrate is
somewhat different. The background granulation
tissue (fibrovascular element) remains
unchanged. In this photomicrograph one can
identify macrophages (yellow arrow) plasma
cells (blue) neutrophils or PMNs (green) This
combination is referred to as subacute
inflammation (mononuclear cells and
granulocytes). What controls this response? The
type of micro-organism does. Certain microbes
stimulate an acute response, others a chronic one
and yet others, a subacute inflammatory response.
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Parulis, acute inflammation
This is a biopsy from a draining fistula or
parulis associated with an abscessed tooth. At
this relatively low magnification one can see a
virtural sea of leukocytes and numerous
capillaries (red arrows). The granulation
tissue here shows no collagen fibers..only
vessels.
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Abscess/Parulis
This higher magnification discloses a few
vessels, some mononuclear cells (very few) and
mostly sheets of neutrophiles or PMNs. This is
what is termed acute inflammation and when
localized under the gingiva it is a submucosal
abscess or parulis. In such an instance, the
pyogenic bacteria coming out of the necrotic pulp
have invaded through bone and out the cortex.
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Apical Periodontal Cyst, low
In some endodontic infections, not only is there
an inflammatory response, but the Rests of
Malassez in the apical PDL are stimulated by
inflammatory cytokines and growth factors
secreted by leukocytes to proliforate. As these
epithelial cells increase in size, they become
necrotic in the center to create a stratified
squamous epithelial lined cavity or cyst. In this
low power photomicrograph, the root tips are
evident at the top of the view and below is a
collapsed cavity. At this power one cannot see
the epithelial lining
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Periapical Cyst, Medium
In this view, one sees the root surface on the
right (we cannot actually see the necrotic root
canal in this section) To the left is an
epithelial lining that still shows proliferation
with cords and strands of anastomosing cells.
Interposed between the cyst and the root is
fibrous connective tissue, a tissue that matured
from preexisting granulation tissue. Adjacent to
the cyst lining are numerous leukocytes.
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APC, Thin Wall
This photomicrograph is a low power view of a
large apical cyst where one can observe the
distended cyst wall, epithelial lining and a
lumen filled with amorphous eosinophilic (pink)
material that represents the cyst contents of
proteinaceous coagulated fluid.
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Inflammation in Wall
This is a higher magnification of the previous
image showing the stratified squamous lining on
the left, fibrous connective tissue wall in the
center, and on the outer edge is an inflammatory
cell infiltrate represented by mononuclear
leukocytes, mostly lymphocytes (Chronic
inflammation).
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Cholesterol Cleft, Multinucleated Giant Cells

• In some apical inflammatory lesions, and for
  reasons not understood, cholesterol accumulates
  in the fibrous and granulations tissues.
• The cholesterol crystallizes into surf-board
  shaped clear cavities.
• They are clear because the processing of the
  tissues for histology uses lipid solvents so all
  we see are ghosts of the material.
• Cholesterol out in the tissues acts as a foreign
  body and one then sees fused macrophages or
  multinucleated foreign body type giant cells
  stretched around the clefts in the process of
  attempted (in vain we think) phagocytosis.

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Pyogenic Granuloma, low mag
Now we will take a look at inflammation out in
the soft tissues of the gingiva and periodontium.
When food particles, popcorn kernals or perhaps
even calculus become entrapped in the gingival
sulcus, they act as an irritant and stimulate an
overzealous proliferation of granulation tissue
accompanied by inflammation. This low power
photomicrograph was obtained from a gingival mass
arising in the interdental papilla. There is
an epithelial layer over the top and the mass is
composed of granulation tissue.
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Pyogenic Granuloma, medium
In this medium power view, we can see an
epithelial layer on the left and on the right,
the mucosal epithelium is lost. This is referred
to as ulceration and the surface is represented
by a fibrin clot with entrapped neutrophils. The
mass is represented by numerous proliferating
blood vessels with intervening loose fibrous
tissue - an excellent example of very vascular
granulation tissue. Leukocytes are distributed
throughout.
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Pyogenic Granuloma, high
This high magnification shows the dilated
vascular channels lined by endothelial cells and
interposed loose fibrous tissue infiltrated with
neutrophils. The term pyogenic implies an
infectious etiology. It is not. The pyogenic
granuloma is a reactive proliferation reacting
to irritation, not infection. This then is an
example of the host inflammatory response forming
in response to injury.
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Mucous Retention PhenomenonLower Lip
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Mucous Escape Reaction
This low power view of a mucocele shows a layer
of surface epithelium and an underlying cystic
mass filled with purple fluid (mucin). Minor
salivary gland lobules are evident on the
lateroinferior margin. The mucocele forms as a
consequence of ductal severage with escape of
secreted mucins into the surrounding connective
tissues.
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Mucocele Wall
When the mucous escapes, it pools and is walled
off by granulation tissue. In this medium power
view, one can observe the mucin on the top,
granulation tissue with underlying dense
collagenous tissue in the center and minor
salivary glands along the bottom.
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Phagocytosis of Mucin
At the interface between the granulation tissue
wall and the pooled mucin, macrophages can be
seen, attempting to phagocytize the mucin. Their
nuclei are round and they have a significant
amount of pink cytoplasm that has a bubbly or
foamy appearance owing to the mucins that have
been ingested by these cells
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Inflammatory Fibrous HyperplasiaDenture
Associated
This low magnification specimen shows a lobulated
mass represented by a partial covering with
epithelium and a massive proliferation of fibrous
tissue below. Collections of minor salivary
tissue were included in the biopsy.
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Inflammatory Fibrous Hyperplasia
This low magnification specimen shows a lobulated
mass represented by a partial covering with
epithelium and a massive proliferation of fibrous
tissue below. Collections of minor salivary
tissue were included in the biopsy.
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Epithelial and Fibrous Hyperplasia
At medium power, it can be seen that the surface
epithelium is thickened or hyperplastic, a
response to trauma from the denture flange. Below
is dense mature collagenous connective tissue.
This connective tissue appears relatively normal
and is traversed by capillaries. Under the
epithelium are a few scattered inflammatory cells.
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Chronic Sclerosing Sialadenitis
The salivary tissues deep in the specimen have
also been traumatized and their secretions have
been blocked leading to degeneration of the
acini. As the acini disappear from apoptosis and
necrosis (forms of cell death), inflammatory
cells infiltrate and phagocytize the necrotic
cells. This is inflammation in response to
injury.
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Chronic Sclerosing Sialadenitis
In this higher magnification, one can see very
few remaining acini, although the ducts are more
resistant to the trauma and the effects of
obstruction. Ductal structures remain in the
absence of acini. The normal tissues are then
replaced by mononuclear inflammatory cells and
the granulation tissue matures into dense fibrous
scar-like tissue. Sclerosis means fibrosis or
scar formation.
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Tuberculosis Ulcer Tongue
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Granulomatous Inflammation
Specific granulomatous inflammation is a special
form of chronic inflammation that is induced be
certain microorganisms, Mycobacterium
tuberculosum being the classic example, although
invasive fungal organisms also cause this type of
inflammation. By definition, chronic
granulomatous inflammation is a chronic
inflammatory reaction in which one sees
collections of granulation tissue (granulomas),
mononuclear inflammatory cells (lymphocytes,
plasma cells, macrophages) and most importantly,
multinucleated giant cells as seen here.
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Tuberculous Granuloma
In this section of chronic granulomatous
inflammation, a collection of multinucleated
giant cells can be seen in the background of
granulation tissue and other leukocytes. These
giant cells form by fusion of macrophages to
create monster phagocytic cells. Certain
glycoproteins on the cell wall of specific
microorganisms play a role in this cell fusion
process.
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Langhans Giant Cell
In TB, the giant cells have a distinctive
appearance. The nuclei are arranged around the
periphery, a wreath-like configuration, and a
smooth pink cytoplasm lies in the center of the
cell. These are Langhans Giant cells. The red
arrows point to individual macrophages from which
the giant cells form. Blue arrows point to
lymphocytes out in the granulation tissue. In
order to actually see the mycobacteria within the
giant cell, we would have to apply an acid-fast
stain.
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Foreign Body Giant Cells
Here are photomics showing suture material and
multinucleated giant cells as well as surrounding
individual macrophages. Note that the nuclei are
dispersed throughout the cytoplasm unlike the
Langhans cells of TB. This entire focus is called
a foreign body granuloma.
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Foreign Body Reaction
Gut and nylon suture are resorbable. In this
section of mouse liver, gut sutures were placed
and after three days, we can see the yellow
filaments of the suture material and surrounding
inflammatory cells. Even at this magnification,
it is easy to see the giant cell reaction in the
upper left.