Diagnostic Cytology
against a d irty background in D iff-Q u ik stain. T his is due to the
hyd rop hob ic inte rac tion between the water-based D iff-Q u ik
stain and the h ig h lip id content w ith in the bacterial cell w all.
T he d iffe re n tia l diagnosis o f tuberculous lym p h ad e nitis o f
m ed iastinal lym p h nodes includes sarcoidosis. Sarcoid granu-
lom as, however, are n o t associated w ith caseous necrosis. Exclu-
sion o f u nd e rlyin g m ycobacterial in fe c tio n (by Z ie h l-N e e lse n
stain and m olec ular studies using polym erase chain reaction)
and clinical c orrelation is essential before a fin a l conclusion o f
sarcoidosis is made. I f p re lim in a ry features suggest g ranulom a-
tous in fla m m a tio n , efforts sho uld be m ade in order to ob tain
a d d itio na l m aterials fo r culture and special studies.
Som e cases o f sem in o m a and n o d u la r sclerosis H odgkin's
lym p h o m a are accom panied b y flo rid g ranulom atous in fla m -
m atio n . O n the o th e r hand, coagulative tu m o r necrosis m ay
Fig. 26.5 Granulomatous lymphadenitis of mediastinal lymph node.
Aggregates of epithelioid histiocytes with "sandal-like” nuclei are seen in asso-
ciation with scanty inflammatory cells and multinucleated Langhans giant cells
(inset). Direct smear of fine-needle aspirate (Papanicolaou x MP and MP [inset]).
som etim es m im ic caseation o n cytologic preparations. Thus,
d ilig en t search fo r suspicious cells is p rud ent before a rrivin g at a
benign cytologic diagnosis.
Nodular Hyperplasia of Thyroid
T h y ro id tissue can be fo u n d anyw here between the base o f
tongue and the aortic arch due to ab norm al m ig ra tio n during
embryogenesis. M ed iastinal th y ro id lesions represent the re tro -
sternal extension o f n o d u la r hyperplasia o f the th y ro id gland
o r intrathoracic th y ro id goiter. C arcinom a arising in ectopic
m ed iastinal th y ro id tissue is extrem ely rare. A case o f H u rth le
cell neoplasm arising in a m ed iastinal ectopic th y ro id and
diagnosed b y fine-needle asp iration b iopsy is o n record.34
Fine-needle asp iration cytology o f retrosternal o r in tra th o -
racic g oiter shows a b enign fo llic u la r pattern com patible w ith
features o f n o d u la r hyperplasia.5,35 Clusters and sheets o f b land-
lo o k in g th y ro id fo llic u la r cells, som etim es arranged in a h on ey-
com bed pattern o r c o llo id -c o n ta in in g fo llic les o f various sizes,
are seen (Fig. 26.6A ) . The background c o llo id m aterial often
dem onstrates a "cracked" o r "sp id er w e b -lik e " appearance,
especially in Giem sa- o r D iff-Q u ik -s ta in e d air-dried smears.
The architectural pattern, w ith p a p illa ry structures containing
secondary follicles, is better appreciated in cell b loc k sections
(Fig. 26.6B ). The th y ro id fo llic u la r o rig in o f the cells can be con-
firm e d w ith im m unocytochem ical study fo r th y ro g lo b u lin o r
th y ro id tra nsc rip tion factor (TTF)-1.
Castleman's Disease
H yaline-vascular and, rarely, plasm a-cell subtypes o f Castle-
m an's disease (synonym : a n g io fo llic u la r lym p h node hyperpla-
sia) seldom present as an a n te rio r m ed iastinal mass. The disease
p rim a rily affects you ng to m iddle-aged adults, w ith no obvious
sex predilection.
Fine-needle asp iration cytology shows a reactive, and som e-
tim es rathe r nonspecific, ly m p h o id pattern, w ith a heteroge-
neous p o p u la tio n o f ly m p h o id cells in tim a te ly adm ixed w ith
loose aggregates o f fo llic u la r d end ritic cells.36 There m ay be large
Fig. 26.6 Retrosternal goiter (nodular hyperplasia of thyroid). (A) Monolayered sheets of bland-looking follicular cells are admixed with colloid material in
the background, compatible with features of nodular hyperplasia of thyroid. Direct smear of fine-needle aspirate (H&E x LP). (B) Broad papillae with colloid-
containing secondary follicles are identified, consistent with nodular hyperplasia of thyroid. Cell block section of fine-needle aspirate (H&E x LP).
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