35
Immunocytochemistry
d iffe re n tia l diagnosis o f effusions, as se n sitivity fo r diagnosis o f
the presence o f m a lig n a n t cells has been reported to be as lo w
as 4 0% .31 It can be used along w ith o th e r a nc illa ry techniques
as w ell. The native cells (m e sothe lial cells) o f the fluid s e xh ib it
a spectrum o f cytom orp holog ic features, w h ic h som etim es
precludes the id e n tific a tio n o f the second p o p u la tio n (foreig n
group) o f cells (Figs 35.6 and 35.7). The m ost c om m o n and
m a jo r practical area in w h ic h IC C plays an im p o rta n t ro le is to
c la rify reactive m esothelial cells versus adenocarcinom a versus
m esotheliom a. Several studies have hig h lig hted o r proposed
a panel o f antibod ies to resolve th is issue. The results o f these
studies indicate th a t the com bined use o f lig h t m icroscopic fea-
tures o f cells in effusions together w ith IC C based o n a
p a n e l
o f
antibod ies com prising b o th m esothelial and adenocarcinom a
m arkers can sig n ific an tly increase diagnostic accuracy.31-33
Im m u n oc ytoc he m istry can be p erform ed o n various cytology
specimens (direct smears— W F A o r acetone), air-dried smears
(fixed w ith alcohol o r postfixed in fo rm o l a lc oh ol), and liq u id -
based
cytology smears
(Th in P rep
and SurePath,
C ytospin
smears, etc.). Storage o f effusions at 4 °C gives a satisfactory
im m u n o h isto c h e m ic a l outcom e w h en a delay in processing
o f the samples is anticipated.34 W e suggest p e rform in g IC C on
10% phosphate-buffered fo rm a lin cell b loc k m aterial, since
the im m u n o re a c tivity pattern o f a variety o f im m u n o m a rke rs is
changed b y d iffe re n t fix a tio n m ethods. Therefore a standardized
m eth od com parable w ith paraffin-em bedded sections can be
applied to cytology specimens to achieve o p tim a l results.
T a b le 3 5 .4
• Sam ple lacks a neoplastic p o p u la tio n
• A n tig e n expression is b e lo w sensitivity o f a n tib o d y
• A n tib o d y co n ce n tra tio n is to o low
• Poor a n tig e n preservation (fixation)
• A n tig e n d iffu sio n (S-100 prote in and gross cystic disease flu id protein-15)
• D en a turation, p ro lo n g e d fixa tion
• In su fficie nt a n tig e n retrieval
• Papanicolaou d e co lo riza tio n
Mesothelial Markers
Based on several studies in the literature, we discuss som e o f
the im p o rta n t m arkers th a t can be used in ro u tin e practice fo r
p ositive id entifications.
Calretinin
T his 2 9-kD a c alcium -b in d in g p ro te in is a m em b er o f th e e lo n -
gation factor hand p roteins, th o u g h t to p lay a ro le in the cell
cycle. It was first reported b y G otzos et al. to be expressed by
A
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F ig . 3 5 .6 Im m u n o re a c tiv ity o f ‘ re a ctive -re p a ra tive ” m e sothelial cells: (A) C A M 5 .2 , (B) d esm in , and (C) c a lr e tin in .
1051
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