27
Kidneys, Adrenals, and Retroperitoneum
Fig. 27.38 Computed tomographic scan demonstrating adrenal
glands (arrows). Right adrenal has an inverted Y shape and is situated behind
the liver. Left adrenal is wedge-shaped and lies behind the pancreas (p) in the
perirenal fat.
T he p itfa lls in diagnosis are as follow s.
• High-grade UC with spindle cells may be confused with
sarcomatoid RCC. The latter may demonstrate a two-com-
ponent pattern with areas of recognizable RCC.
• UC with either glandular or squamous differentiation may
be confused with tumors metastatic to the kidney, such
as bronchogenic carcinomas, and may be impossible to
distinguish cytologically.
• Distinction from UC or its papillary variant is based on
the distinctive nuclear and cytoplasmic features of each
entity as well as the characteristic foamy histiocytes, psam-
moma bodies, and hemosiderin pigment found in PRCC
(discussed earlier). Distinction from CDC is more difficult
(discussed earlier).
• Distinction of UC from high-grade RCC may be diffi-
cult and is based on the presence of focal areas of RCC
that may be better differentiated, with clear cell fea-
tures, lower nucleocytoplasmic ratios, and fewer hyper-
chromatic nuclei. Special stains for RCC antigen will be
negative in UC and positive in RCC, while mucin and car-
cinoembryonic antigen are helpful because RCC does not
express either whereas UC may be positive for both. UC
can occasionally coexist with RCC in the same kidney.
• Reactive urothelial cells in the presence of a filling defect
of the renal pelvis due to a blood clot or kidney stones
may be overdiagnosed as low-grade UC. Extreme cau-
tion should be exercised in the presence of a specimen
containing only few urothelial cells or cell groups with
enlarged nuclei, smudgy chromatin, and several nucle-
oli indicative of reactive or regressive cell change, with a
request for a surgical biopsy or frozen section before
definitive therapy.
• Interphase FISH using a cocktail of probes for chromo-
somes 3, 7, 17, and 9p21.3 can be extremely helpful to
differentiate reactive urothelial cells versus low-grade
UC on an FNA. A large percentage of low-grade UCs will
have chromosomal abnormalities sufficient for a positive
FISH diagnosis of carcinoma, namely four or more ab-
normal cells as demonstrated by polysomies for chromo-
somes 3, 7, or 17 or twelve or more cells with deletions of
9p21.3.113.112
Key features of urothelial carcinoma
• Forms 7% of all renal neoplasms;
• Significant association with the occurrence of urothelial
tumors of other sites;
• Exophytic and papillary tumors, less commonly
infiltrative;
• Exophytic tumors are usually low grade and flat;
• Infiltrative tumors are high grade;
• Low-grade UC—cells are columnar or polygonal with
a moderately dense and amphophilic cytoplasm;
• Tumor cells with cytoplasmic tails, "cercariform" cells,
may be present in intermediate and high-grade tumors;
• High-grade UC—columnar or polygonal cells,
pleomorphism, and increased mitotic activity;
• Bizarre multinucleated giant cells, spindle cells, and
squamous differentiation can be seen in high-grade
tumor;
• Positive for low and high molecular weight CK,
thrombomodulin, and uroplakin; and
• Interphase FISH using a cocktail of probes for
chromosomes 3, 7, 17, and 9p21.3 can be useful for dis-
tinguishing benign from malignant urothelial cells.
Squamous cell carcinoma
Sq uam ous cell carcinom a is th e second m o st fre q u e n t ep i-
th e lia l m alig n a n c y o f th e ren al pelvis. It affects b o th sexes
e q u a lly and occurs m o st c o m m o n ly in th e s ix th and seventh
decades o f life . B oth kidneys are e q u a lly affected. A ssoci-
ated renal calculi have been observed in as m a n y as 5 7% o f
rep orted cases.108 T h e tu m o rs are m o s tly fla t and in filtra tiv e .
A t th e tim e o f d iagnosis, m o s t p atients have invasive disease.
T h e p rognosis is g e ne rally p o o r, and a m ed ian su rviva l is
5 m on ths.
Fine-needle asp iration reveals irreg ular clusters o f m a lig n a n t
squam ous cells.
Adenocarcinoma
A denocarcinom a is an extrem ely rare neoplasm and lith ia sis
is observed in a h ig h percentage o f cases. C h ron ic in fla m m a -
tio n and g land ular m etaplasia m ay be associated signs. H is to -
logically, the pattern m ay be p a p illa ry o r com posed o f signet
rin g cells. M an y tu m o rs bear a strikin g resemblance to colonic
adenocarcinom as. M u c in p rod u c tio n m ay vary fro m scant to
abundant.
Very few reports on the cytology o f th is e n tity exist.15 The
gross appearance o f the aspirate m ay be a y e llo w -w h ite sem i-
transparent m ucinous substance. Single o r clustered m a lig n a n t
g land ular cells m ay be present.
Adenosquamous carcinoma
Fine-needle asp iration find ing s o f m ixed adenosquam ous carci-
n om a o f the renal pelvis are indicated b y the presence o f m alig -
n an t squam ous and g land ular cells.15
843
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