25
Breast
can arise fro m b enig n cystic changes as w e ll as fro m n o rm a l
lob ules
and
ducts.272
T he
d iffe re n tia l
diagnosis
includes
m ucocele-like lesions
th a t c on tain occasionally ab und ant
m u c in w ith a fe w clusters and sheets o f regular ductal epi-
th e liu m th a t lack nuclear atyp ia.272 Fib road enom a m ay show
m yxo id change in th e strom a, w h ic h can be m isinte rp rete d as
m u c in (Fig. 2 5.2 5 ). However, fib roa d en om a generally presents
Fig. 25.45 Scattered stripped malignant nuclei in an aspirate of medullary
carcinoma (Diff-Quik x HP).
in a you ng e r age group and has cytologic features o f cell clusters
w ith fing e r-like b ranching, m a n y naked b ip o la r nuclei in the
background, and strom a l fragm ents. Several studies have com -
pared th e u tility o f b o th FN A and CNB in d iffe re n tia tin g b enign
fro m m a lig n a n t m uc in ou s breast lesions. These studies con-
clude th a t core b iop sy is m ore relia b le and accurate th a n FN A
fo r th e diagnosis o f m uc in ou s lesions o f the breast.29,273,274
Key features of mucinous (colloid) carcinoma
• Abundant pools or strands of mucin;
• Aggregates and cell balls of tumor cells, often uniform in
appearance, along with isolated tumor cells; and
• Occasional malignant signet ring cells.
Tubular (Well-Differentiated) carcinoma
T u b u la r carcinom a in its pure fo rm tends to be relative ly sm all,
in the size range o f 1 cm o r less. The lesio n can be m u ltic e n -
tric and b ilateral. Lym ph node metastasis occurs in o ne -third
o f the patients, b u t th e overall prognosis, even w ith m etastatic
disease, is excellent. T his is a no the r breast carcinom a th a t can
be underdiagnosed in FN A b iop sy o w in g to the relative ly u n i-
fo rm appearance o f the tu m o r cells, w h ic h m ay show o n ly m ild
atypia.86,275-279 T he diagnosis m ay be suspected w h en groups
o f atypical m o n o m o rp h ic cells are arranged in angulated,
rig id g land ular o r tu b u la r structures, inc lu d in g som e having
C
Fig. 25.46 (A) Aspirate of a cystic medullary carcinoma consisting of fragments of neoplastic cells with associated chronic inflammatory cells admixed with
hemorrhagic fluid in this cell block (H&E x LP). (B) High-power examination of a cell block from an aspirate showing loose clusters of malignant cells associated
with numerous chronic inflammatory cells. Clinically this was a cystic lesion (H&E x HP). (C) Scattered high-nuclear grade malignant cells in an aspirate of a
cystic medullary carcinoma (Diff-Quik x HP).
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