ON
C
Fine-Needle Aspiration of
Various Organs and Body Sites
chapter
26
Mediastinum
Wai-Kuen Ng
Contents
In tro d u c tio n
E m b t y o n a l C a r c in o m a
A n a to m ic C o m p a r tm e n t s a n d C lin ic a l C o r r e la t io n
Y o lk S a c T u m o r
R o le s o f F in e - N e e d le A s p ir a t io n C y t o lo g y
C h o r io c a r c in o m a
T e c h n ic a l C o n s id e r a tio n s
N o n -n e o p la s tic L e sio n s
P rim a i
y
M e d ia s tin a l L a rg e B -c e ll L y m p h o m a
B e n ig n M e d ia s t in a l C y s ts
A n a p la s tic L a rg e -C e ll L y m p h o m a
R e a c tiv e M e s o t h e lia l H y p e rp la s ia
H o d g k in 's L y m p h o m a
R e a c tiv e L y m p h o id H y p e rp la s ia
N e u r ile m m o m a a n d N e u r o f ib r o m a
A c u te M e d ia s t in it is a n d C h r o n ic S c le ro s in g M e d ia s t in it is
N e u r o b la s t o m a , G a n g lio n e u r o b la s t o m a , a n d G a n g lio n e u r o m a
G r a n u lo m a t o u s L y m p h a d e n it is
P a r a g a n g lio m a
N o d u la r H y p e rp la s ia o f T h y r o id
S o ft T is s u e T u m o r s
C a s tle m a n 's D is e a s e
F o llic u la r D e n d r itic C e ll S a r c o m a
E x t r a m e d u lla r H e m o p o ie s is
P a r a th y r o id A d e n o m a
N e o p la stic L e sio n s
M e t a s t a t ic C a r c in o m a s
T h y m o m a
D ia g n o s tic p itfa lls a n d A lg o r it h m s
T h y m ic C a r c in o m a
D ia g n o s tic P itfa lls a n d P ra c tic a l P o in t s
T h y m ic N e u r o e n d o c r in e T u m o r s
D ia g n o s tic A lg o r it h m s
S e m in o m a
C o n c lu d in g R e m a rk s
Introduction
Anatomic Compartments and Clinical Correlation
T he m ed iastinum is a large anatom ic com p artm ent in the th o -
racic cavity, b ound ed la te ra lly b y the pleurae, a n te rio rly b y the
sternum , p o steriorly b y the vertebrae, sup e rio rly b y th e thoracic
in le t, and in te rio rly b y th e diaphragm . It is fu rth e r subdivided
in to fo u r a rb itra ry p o rtio ns b y the pericardium , nam ely, supe-
rio r, anterior, m iddle, and p osterior com partm ents. The sup erior
m ed iastinu m lies above the pericardium . T he a n te rio r m ed iasti-
n u m is b ounded p o steriorly b y th e pericardium and a n te rio rly
b y the sternum . The m id d le m ed iastinu m is surrounded by the
fib rous pericardium . The p osterior m ed iastinum is the space
lyin g between the pericardium and lo w e r thoracic vertebrae.
T his sub d ivision is useful especially in rad iolog ic d iffe re n tia l
diagnosis, as certain m ed iastinal lesions occur p refere ntially in
one lo c a tio n (Fig. 2 6.1) .
M ed iastinal lesions are o fte n asym ptom atic and discovered
as incid ental finding s o n rad iolog ic e xa m in ation fo r o th e r p ur-
poses. W h e n sym ptom s (e.g. dyspnea, dysphagia, sup erior vena
cava syndrom e) appear, th ey are u su ally due to a pressure effect
as a result o f im p ing e m e n t o f adjacent v ita l structures. Taking
the anatom ic lo c a tio n o f the lesion and age o f the p a tie nt in to
consideration, a n a rro w lis t o f d iffe re n tia l diagnosis can often
be produced even before fine-needle asp iration biopsy.
In adults, the com m onest m ed iastinal lesions are metastasis
and benign m ed iastinal cyst o f celom ic o r gastroenteric orig in.
T h y m o m a represents the com m onest p rim a ry th ym ic tu m o r
occurring in adults, fo llo w e d b y m ed iastinal lym p h o m a . T h y -
m o m a is associated w ith a w id e range o f clinical syndrom es
inc lu d in g m yasthenia gravis. In children, the c om m onest th ym ic
tu m o r is non -H od g kin's lym p h om a. T h y m o m a is extrem ely rare
in child hood . M ed iastinal germ cell tu m o rs account fo r up to
16% o f m ed iastinal neoplasm s in adults and about 1 9 -2 5 % o f
m ed iastinal tu m o rs in children. A n association between m ed i-
astinal non se m in om atou s germ cell tu m o rs and K linefelter's
syndrom e and hem atolog ic m alignancies has been observed.
N eurogenic tu m o rs (in c lu d in g n e u rile m m o m a , n eurofib rom a,
m a lig n a n t peripheral nerve sheath tu m o r, neuroblastom a, gan-
glioneurob lastom a, g ang lioneurom a, and paragangliom a) are
u su a lly located in the m id d le and p osterior m ed iastinum , w here
th ey constitute the m ost freq uent neoplasms. N eurob lastom a
and g ang lioneurob lastom a occur m a in ly in child hood .
Roles of Fine-Needle Aspiration Cytology
The applications o f fine-needle asp iration cytology in the
m ed iastinum are m a in ly as follow s:
• Establishing a primary pathologic diagnosis, or at least
separating nonsurgical from surgical cases;
• Lymph node staging of primary lung cancer and assess-
ing operability; and
• Detecting residual disease or recurrent tumor after
therapy.
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