PART TWO
Diagnostic Cytology
Fig. 25.63 (A) Aspirate of metaplastic carcinoma showing
chondrosarcomatous differentiation characterized by scattered oval
malignant cells enmeshed in a metachromatically staining myxoid
stroma (Diff-Quik x LP). (Inset) Scattered mononuclear and binucleated
oval malignant cells in metaplastic carcinoma demonstrating
chondrosarcomatous differentiation (Papanicolaou x HP). (B) Corresponding
histologic section showing chondrosarcomatous differentiation in a
metaplastic carcinoma (H&E x MP).
tu m o rs metastasize. Assessment o f patients begins w ith the c lin -
ical exa m in ation , because phyllodes tu m o r often presents as a
large tu m o r m easuring greater th an 4 cm in m a x im u m diam eter.
C ytolog ic d istin c tio n o f phyllodes tu m o r fro m fib road enom a
has been p re d o m in a n tly based on assessment o f the cellular-
ity o f the strom a l fragm ents.352,367-371 Linsk and colleagues com -
m ented th a t h ig h ly cellular strom al fragm ents favor phyllodes
tu m o r, in contrast to the relative ly lim ite d strom a c e llu la rity o f
fib road enom a in FN A specimens (Fig. 25.6 6 ).372 O thers believe
th a t hyp ercellular strom a l fragm ents can be seen in b o th phyl-
lodes and fib road enom a, w ith o u t any d isc rim in a to ry value.174
A n o th e r h e lp fu l c rite rio n favoring phyllodes tu m o r is the pres-
ence o f spindle-shaped strom a l cells enm eshed in p ink-stainin g
m a trix w ith m etachrom atic stains.372,373 In fact, Sneige and
Singletary believe th a t the FN A diagnosis o f benign phyllodes
tu m o r and occasionally phyllodes tu m o r o f lo w m alig n an t
p o te n tia l diagnosis sho uld be based on the appearance o f the
in d ivid u a l strom a l cells instead o f strom a l cellularity, because the
la tte r m ay be overestim ated ow in g to th ic k tissue fragm ents.28 In
phyllodes tu m o r, th e strom al cells are elongated and have long
spindle nuclei w ith irreg ular nuclear m em branes and occasional
n uc le oli, in contrast to the b ip o la r naked nuclei o f strom a l cells
o f fib road enom a.174,374 C ytolog ic d iffe re n tia tio n o f benign fro m
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Fig. 25.64 (A and B) Squamous cell carcinoma of the breast: aspirate
shows cohesive groups of malignant keratinized and spindle cells. The lesion
was not attached to skin and there was no prior history of malignancy. These
findings are consistent with primary squamous cell carcinoma of the breast.
(Papanicolaou x HP.)
m a lig n a n t phyllodes tu m o r is based on the presence o f atypical
strom al cells (Fig. 25.6 7 ). Increased c e llu la rity w ith atypia and
m itoses suggest m a lig n a n t phyllodes tu m o r.9 P53 was proposed
to help the d iffe re n tia l diagnosis.368
Key features of phyllodes tumor
• Cellular smears;
• Biphasic population of epithelial and stromal cells;
• Hypercellular stromal fragments consisting of spindle-
shaped cells present singly and enmeshed in metachro-
matically staining stroma;
• Stromal cell atypia is a feature of malignant phyllodes
tumor;
• Epithelial hyperplasia can be present;
• Numerous bipolar naked nuclei; and
• Occasional cases indistinguishable from fibroadenoma.
In o u r in itia l experience w ith phyllodes tu m o r, various
degrees o f e p ith elial p ro life ra tio n were encountered, inc lu d in g
three cases show ing sig nificant e p ith elial atypia (Fig. 2 5.6 8 ).352
P ro m in e n t e p ith elial com p onent can be seen in b o th benign
and m a lig n a n t phyllodes tu m o r, and in occasional cases the
degree o f e p ith elial p ro life ra tio n could p o te n tia lly lead to a
false-positive diagnosis o f breast carcinom a (Fig. 2 5.6 9 ). H e lp fu l
754
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