PART TWO
Diagnostic Cytology
Fig. 26.1 Occurrence of various non-neoplasticandneoplasticlesionsin
different anatomic compartments of mediastinum.
In general, fine-need le a sp iratio n b iop sy is considered a
rapid, h ig h ly reliab le, and w e ll-to le ra te d procedure in diag-
nostic e va lu a tio n o f neoplastic m ed iastina l lesions presenting
as sup e rio r vena cava synd rom e.1
C yto m o rp h o lo g ic assess-
m ent, tog ether w ith c lin ic o ra d io lo g ic c o rrelatio n and a n c illa ry
investig ations (in c lu d in g im m u n o c y to c h e m is try and electron
m icroscopy), can p rovid e useful in fo rm a tio n and achieve h ig h
diagnostic accuracy.2-5 T he presence o f a p a tho lo g ist o n site
helps to assess specim en adequacy and o p tim ize s th e selec-
tio n o f tissue sam ples fo r a n c illa ry investigations. Som etim es,
o b ta in in g adequate sam ple in fine-need le asp iratio n o f m ed i-
a stin um m ay n o t be easy, as som e m ed iastina l lesions are
associated w ith extensive necrosis, strom a l sclerosis, o r cystic
changes, resu ltin g in p aucicellular yie ld . I f feasible, reserv-
ing som e m aterials fo r cell blocks is also h e lp fu l, p a rtic u la rly
fo r a nc illa ry studies, w h ic h includ e im m u n o c y to c h e m is try
(Table 2 6 .1 ), electron m icroscopy, o r m ole c u la r analysis. In
expert hands, electron m icroscopy can p rovid e h e lp fu l clues
in diagnosing m ed iastina l neoplasm s, especially i f th e tu m o r
cells are u nd iffe ren tia te d , scanty, o r p o o rly preserved b y lig h t
m icroscopy.6-9
Even th o u g h d e fin itive diagnosis m ay n o t be possible on
som e occasions, p re lim in a ry inte rp reta tion s m ay help to guide
th e c lin ic ia n in p la n n in g a subsequent m anagem ent approach.
Som e authors have show n th a t b o th fine-needle asp iratio n and
core biopsies carry s im ila r sensitivities in diagnosing m edias-
tin a l lesions. T he typ ing accuracy o f core biopsies, however, is
s lig h tly better,10,11 especially fo r noncarcinom atous lesions.12
Som e centers ap p ly endoscopic ultrasound -g uid ed fine-needle
asp iration and core biopsies sim u lta n e o u sly so th a t b o th con-
v e n tio n a l cytologic preparations and tissue sections can be
exam ined.
Technical Considerations
T he techniques o f fine-need le a sp iratio n and sam ple prepa-
ra tio n fo r m ed iastina l lesions in general are s im ila r to those
fo r lesions at o th e r sites. H ow ever, o w in g to th e special loca-
tio n o f th e m e d ia stin u m , fine-need le a sp ira tio n biopsies
are o fte n p e rform ed u n d e r fluoroscop ic, com p uted to m o g -
raphy, o r u ltra s o u n d guidance. C o m p ute d to m o g ra p h y has
th e advantage o f accurately loc atin g even s m a ll m ed iastina l
masses and is especially useful in g u id ing fine-need le aspi-
ra tio n b iopsies o f lesions in th e th oracic in le t, h ilu m , and
m id d le m e d ia stin u m v ia a supraclavicular, suprasternal, o r
parasternal approach. T he ro u te o f th e asp irating needle can
be p lanned m o re precisely in o rd e r to avoid vascular struc-
tures. O n th e o th e r hand , u ltra s o u n d can p rovid e b o th spa-
tia l o rie n ta tio n and c o n tin u o u s re a l-tim e m o n ito rin g w ith o u t
ra d ia tio n exposure. Fine-need le a sp ira tio n biopsies o f m e d i-
a stinal lesions are p e rform ed v ia th e percutaneous ro u te
(u n d e r com p uted to m o g ra p h y o r u ltra s o u n d guidance), b ro n -
choscopy o r esophagoscopy (u n d e r u ltra s o u n d guidance), o r
m ediastinoscopy.
Transb ronchial o r transesophageal endoscopic u ltrasound -
guided rea l-tim e fine-needle asp iration is becom ing increasingly
p o p ular and spares the patients fro m m ore invasive m ethods
such as m ediastinoscopy. It is considered a m in im a lly invasive
procedure and can be p erform ed und er conscious sedation in
an o u tp a tie n t setting. T he diagnostic accuracy fo r m alignancy
in m ed iastinal lesions is h ig h w h e n applying endoscopic
ultrasound-guided
fine-needle
a sp iratio n .13-16
Endoscopic
u ltra sou nd is capable o f b o th characterizing the lesion and
guid ing the fine-needle asp iration procedure in real tim e using
a "th ro u g h the scope" needle-aspiration system. This technique
has supplem ented c onventional com puted tom ography-guided
transthoracic fine-needle asp iration b iopsy in evaluating m ed i-
astinal lesions, especially fo r those lyin g deep in th e m ed iasti-
n u m (in c lu d in g subcarinal region and p o sterior m ed iastinu m ).
Endoscopic ultrasound-guided fine-needle asp iration is also
h ig h ly effective in o b tainin g tissue samples even fro m sm all
lesions.17 T his technique, especially w h en coupled w ith im m e -
diate cytologic evaluation, can im p rove the cellular y ie ld and
achieve h ig h diagnostic accuracy in the evaluation o f enlarged
m ed iastinal lym p h nodes.18,19
The m a in lim ita tio n o f transb ronchial fine-needle aspira-
tio n is the re la tive ly h ig h incidence o f false-negative diagnosis.20
Som e authors suggest th a t w h e n sam p ling m ed iastinal lym p h
nodes via the transb ronchial route, the presence o f lym phocytes
in transb ronchial needle aspirates o f m ed iastinal lym p h nodes
is an essential c rite rio n fo r assessing specim en adequacy.21
Negative specimens lacking lym phocytes sho uld be considered
unsatisfactory.
C o m p lications o f m ed iastinal fine-needle asp iration biopsies
are u su ally m in o r.3,22 The com m onest com p lica tion is p n eu m o -
thorax, b u t o n ly a few patients require in se rtio n o f a chest drain.
M in o r hem optysis m ay also occur in som e patients after the
procedure. M ed iastinal fine-needle asp iration is considered safe
even i f sup erior vena cava o b struction is present.
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