CHAPTER 17
Endocrine System
333
A
Acidophils
Pleomorphic
nucleus
Interstitial
blood
Tumor cells
Normal
Prolactinoma—H&E
Figure 17-7A,B.
Pituitary Adenoma. A
:
H&E, (
left
)
3
213; (
right
)
3
154.
B
: Immuno-
cytochemistry, (
left
)
3
213; (
right
)
3
154
Pituitary adenomas
are benign tumors of the
anterior pituitary gland. Clinically, they can be
divided into nonsecreting and secreting forms.
Historically, adenomas were classiF ed by their
staining properties, the degree to which they
took up the stains hematoxylin and eosin. They
were classiF ed as
basophilic
,
acidophilic
, or
chromophobic adenomas
. With modern immu-
nocytochemical techniques, however, tumor
cells can be classiF ed by the type of hormone
they produce. Some cells do not mark with any
antibody, and their tumors are called
null-cell
adenomas
. Pituitary tumors may compress the
hypothalamus, cranial nerves, or the optic chi-
asm. A
bitemporal hemianopia
is commonly
seen in patients suffering from compression of
the optic nerve. Mutations are believed to play
a role in the development of the tumors. Patho-
logically, the tumors are composed of uniform,
polygonal cells arrayed in sheets or cords. They
lack a reticular network of supporting connec-
tive tissue and show
monomorphism
. Treatment
includes drug therapy and surgery, depending
on the type and the size of the tumors.
A:
The
prolactinoma
lacks acidophils and has tumor
cells with
pleomorphic nuclei
(variable size
nuclei). The normal tissue of the pars distalis of
the pituitary gland shows individual or clusters
of acidophils interspersed among basophils and
chromophobes (
right
).
B:
The cell membranes
of
prolactin-producing tumor cells
have been
stained brown using an immunocytochemical
reaction. The majority of the cells in this sample
are tumor cells. By contrast, in the normal tissue
sample shown on the
right
, only a small number
of prolactin-producing cells are stained.
Figure 17-7C.
Pituitary Adenoma in Magnetic Resonance
Imaging.
Pituitary tumors
, called
adenomas
, can be classiF
ed accord-
ing to their size, secretory status, histology, and general
clinical picture of the patient. Regarding size, they can be
microadenomas
, which are less than 1 cm in size (about 50%
of all tumors at diagnosis) and may be difF
cult to remove,
and
macroadenomas
, which are greater than 1.0 cm in
diameter, and may cause deF
cits related to hormone imbal-
ance or compression of adjacent structures. ClassiF
cation
by secretory status may refl
ect, for example, excess
cortisol
(
Cushing disease
) or
prolactin
(
prolactinoma
) or the over-
production of
growth hormone
(
gigantism
or
acromegaly
).
The MRI may refl
ect damage to the hypothalamus; the optic
chiasm, nerve, or tracts; or increased intracranial pressure.
Histologic classiF
cation relies on demonstrating particular
abnormal cell types in biopsy samples.
CLINICAL CORRELATIONS
C
Tumor
B
Normal
Tumor cells
Prolactin-producing
cells
Prolactinoma—immunocytochemistry
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