Diagnostic Cytology
Fig. 27.24 (A) Mucinous, tubular, and spindle cell renal cell carcinoma showing densely cellular fragments of small cells and numerous naked
nuclei adjacent to sheets. (B) Cells with round to oval nuclei representing the tubular component. (Papanicolaou x LP) (spindle cell component x LP;
C, Papanicolaou; D x HP.)
m ost sig nificant prognostic factor and the m edian survival was
reported as 6.8 m onths. In the M D A C C series, Auger and col-
leagues reported on the m orp h olog ic and im m unocytochem ical
features o f 15 cases o f sarcom atoid RCC (9 p rim a ry tu m o rs and
6 m etastases).94 A ll cases w ith an e p ith elial c om p onent showed
high-grade nuclear features. T he spindle cell com p onent was
fibrosarcom atous, M FH , o r unclassified;94 85% o f the spindle
cell c om p onent stained p o sitively fo r CK.
T his carcinom a appears as clusters o r single cells w ith either
clear o r granular cytoplasm and o f variable nuclear grade, w ith
the cytologic appearance o f RCC (Fig. 2 7.2 7 ) adm ixed w ith cells
cytolog ically consistent w ith sarcoma. The sarcom atoid cells
are large and spindled and fre q ue ntly occur in large aggregates
o r dense, tig h tly coherent fragm ents (Fig. 27.2 8 ). T he nuclear
features o f the sarcom a cells are always h ig h grade; the cells
are hyperchrom atic, w ith p ro m in e n t n uc le oli, and often have
m ultinucleated , p leo m o rp hic form s. O steoclastic g iant cells
m ay be present (Fig. 27.2 8 , inset). Im m u n oc ytoc he m istry stains
m ay show the sarcom atoid cells to be keratin- and EM A-negative
and vim en tin-p o sitive. In m ost cases, however, the sarcom a-
to id cells are keratin (A E 1/A E 3) o r EM A-positive. The sm o oth
m uscle actin stain and v im e n tin m ay be p ositive in these spindle
Differential Diagnosis
There are som e diagnostic pitfalls. The diagnosis o f sarcom atoid
RCC b y FN A m ay be overlooked i f just the sarcom atoid com po-
n en t is aspirated, resulting in diagnosis o f a sarcoma. S im ila rly,
i f the carcinom atous c om p onent is the o n ly com p onent aspi-
rated, a diagnosis o f RCC is made. D iffe re n tia tin g sarcom atoid
RCC fro m high-grade RCC m ay also be d iffic u lt. A diagnosis o f
a high-grade RCC (nuclear grade IV ) is m ade in the presence
o f a p leo m o rp hic e p ith elial com p onent w ith o u t a sp indle cell
com ponent.
Use o f cell blocks to elucidate the architectural features fu r-
th e r and th e periodic a c id -S c h iff (PAS) stain (w ith and w ith -
o u t diastase) to dem onstrate glycogen m ay aid in discerning a
sm all RCC c om p onent on FNA. A d d itio n a lly, e xa m in ation o f
cells u ltra stru c tu ra lly and b y im m u n o h is to c h e m is try m ay assist
in d em onstrating tw o com ponents.
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