310
UNIT 3
Organ Systems
Figure 16-4A.
Parotid glands.
H&E,
3
295; inset
3
97
Parotid glands
contain only serous secretory cells. There
are some adipose cells scattered throughout the gland. All
three types of salivary glands have similar duct systems. The
intercalated ducts are shown here; they have a small lumen
and are lined by lower cuboidal cells with basally located
nuclei. The
inset
shows a large interlobular duct that is
lined by
stratif ed columnar cells
and is surrounded by a
large amount of connective tissue. The diameter of the ducts
gradually increases from the intercalated ducts to the large
interlobular ducts, and their lining cells increase in height
and in number of layers (see Fig. 16-3A). The main duct
(
duct o± Stenson
) of the parotid gland traverses the buccina-
tor muscles and opens opposite the secondary upper molars
(see Fig. 16-1). All three types of salivary glands receive
para-
sympathetic
innervation. The parotid gland is innervated by
the
glossopharyngeal nerve
(
cranial nerve [CN] IX
).
Adipose
Adipose
cells
cells
Adipose
cells
Interlobular
Interlobular
duct
duct
Interlobular
duct
Intercalated
Intercalated
duct
duct
Intercalated
duct
Serous
Serous
cells
cells
Serous
cells
Intercalated
Intercalated
duct
duct
Intercalated
duct
A
CLINICAL CORRELATIONS
Figure 16-4B.
Pleomorphic Adenoma.
H&E,
3
55
Pleomorphic adenoma
, also called
benign mixed tumor
,
is the most common benign salivary gland tumor. The
majority, approximately 80%, occur in the parotid gland,
most of which are in the super± cial lobe, and are benign
pleomorphic adenomas. The tumor may also involve
submandibular, sublingual, and minor salivary glands. It
is characterized by a slow-growing, mobile, and painless
parotid mass. Most patients are not aware of the tumor
for years. The mass itself is typically well demarcated, but
may be nodular in appearance. Histologically, the neo-
plasm is composed of epithelial and
myoepithelial cells
in
a
chondromyxoid background
. Fine needle biopsy is use-
ful in the diagnosis of pleomorphic adenoma. After sur-
gery, pleomorphic adenomas may recur. Rapid growth
of a mass in the same area after surgery may signify
malignant transformation of the residual adenoma called
carcinoma expleomorphic adenoma
. This photomicro-
graph shows nests of
myoepithelial cells
in a
myxoid
background
.
Figure 16-4C.
Parotid Cyst.
H&E,
3
11
A
parotid cyst
is a fl uid-±
lled closed cavity occurring
within the parenchyma of the parotid gland and is usu-
ally caused by trauma, infections, salivary gland stones,
or tumors. Physical exam usually reveals a painless
lump or swelling. As the cyst enlarges, it may interfere
with chewing, swallowing, and speaking. Additionally,
parotid cysts may become infected. Histologically, the
cyst is lined by an epithelium, and the cavity is ±
lled
with fl
uid or mucus. The surrounding
stroma
shows
dense ±
brosis and may be in±
ltrated by aggregates of
lymphocytes, as shown in this slide. If necessary, surgical
removal of the cyst is recommended.
Myoepithelial
cells
Myxoid
background
B
Parotid
gland
Cyst
Stroma
C
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