BREAST CYTOPATHOLOGY

58 3. Benign and Borderline Tumors
Cytomorphologic Characteristics
(Figures 3.1 to 3.8)
• Grossly, the aspirate may appear sticky and tenacious,
often clogging the needle lumen.
• Smears are often hypercellular with a characteristic
biphasic appearance (epithelium and mesenchymal/stromal
tissue).
• Epithelium appears as cohesive, usually monolayered
sheets of well-organized ductal-type epithelium, often with
foldings, branchings with a “papillarylike” architecture
(“staghorn”) or even tubular.
• Naked bipolar myoepithelial nuclei are noted scattered in
the smear background in a significant number of cases.
These have the so-called rice grain morphology and are
best visualized in Papanicolaou-stained smears.
• Variably cellular fibrous stromal fragments are present.
• Chondromyxoid stroma is present, often with a bright
metachromatic or magenta-colored appearance on Diff-
Quik–stained smears and less obvious on Papanicolaoustained
smears (pale green).
• Juvenile fibroadenomas tend to have a more monomorphic
appearance with predominantly larger epithelial fragments
of a blander uniform columnar type. A papillary architecture
can be a prominent feature.
• Uncommon features include significant epithelial atypia
(nuclear enlargement, crowding, pleomorphism, and prominent
nucleoli), apocrine and foam cells, prominent mucinous
change, multinucleated giant cells, and lack of a
stromal component (see Figures 3.5 to 3.8).
Pitfalls and Differential Diagnosis
• Fibrocystic changes
• Atypical ductal hyperplasia
• Intraductal papilloma, papillary carcinoma
• Pyllodes tumor