PART TWO
Diagnostic Cytology
Fig. 27.12 Conventional renal cell carcinoma (RCC) showing granular cell component (Papanicolau, x LP). (B) Cell block with granular cell component
(x LP). (C) Clear cell RCC component (Papanicoloau x LP; cell block, clear cell RCC x LP).
m ay coexist in 15% o f tu m o rs.3 Four cytologic grades are
proposed, based on Furhm an's nuclear grading system ,65 w h ic h
is easily applicable to cytologic specimens (Table 27.4 and Figs
27.10 and 27.11). Tum ors com posed o f clearly defined areas
o f high-grade spindle cells interspersed w ith cells o f RC C are
designated as sarcom atoid RCCs and considered a separate
e n tity (discussed later).
Im m unocytochem istry
C le a r cell R C C ty p ic a lly has a very lim ite d C K expression p ro -
file, w ith p re d o m in a n t expression o f CKs-8, -18, and C A M 5.2
and IH C -4 4 . CK-7 expression is u n c o m m o n , rang ing fro m
o n ly 5% to 20% in several studies, w ith an overall expression
rate o f 9% . C lear cell RCCs are u su a lly p o sitive fo r e p ith e lia l
m em b rane antigen (E M A ). V im e tin is u su a lly p o sitive in clear
cell RCC to th e extent o f 65% . C lear cell RCCs sho w a h ig h
rate o f expression o f C D 10 (Fig. 2 7 .1 3 ). W h ile chrom o p ho b e
RCC can also be occasionally p o sitive fo r C D 10, th e o verall
C D 10 expression in c hro m o p h o b e RCC is 26% , in contrast to
8 6% in clear cell RCC. RCC M a is also p o sitive in m o re th a n
8 0% o f clear cell RCCs and is u su a lly negative in a ll o th e r
types o f RCC.45 PAX2 is present in lo w to in te rm e d ia te grades
o f RCC.
Key features of clear cell RCC
• Most common variant of RCC;
• Contains different cell types exhibiting variable degrees of
nuclear pleomorphism and mitotic activity;
• Clear cells with abundant, fragile, and vacuolated
cytoplasm;
• With or without granular cells with a moderately dense
and granular eosinophilic cytoplasm;
• Positive for EMA, vimentin, and CD10, and infrequently
positive for CK-7; and
• Common cytogenetic alteration is loss of short arm of
chromosome 3 (3p-) VHL gene.
Chromophobe Cell Renal Carcinoma
C h rom op h o b e cell renal carcinom a, described first h is to lo g i-
cally b y the G erm an p atholog ist Thoenes40,77 and subsequently
in o th e r studies,78,80 was described in 1995 in the FN A cytology
lite rature.81,82 Because o f its possible confusion w ith oncocytom a
b y FN A and its m a lig n a n t b iolog ic behavior, CCRC is ric h ly
deserving o f recog nition. CCRC has a reported incidence o f 4%
o f all e p ith elial renal tu m o rs.13 In Thoenes and colleagues' study
o f 3 2 cases, the age range was between 31 and 75 years, w ith
824
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