| Anatomy and histology of the breast |
| Nipple discharge cytology |
| Fine needle aspiration (FNA) |
| Reporting terminology |
| Evaluation of the specimen |
| Benign lesions |
| Breast carcinoma |
| Phyllodes tumor |
Fibrocystic change
Fibrocystic change is the most common lesion to produce a breast mass in women aged over 30. Up to 50% of women have palpable 'lumpiness' and up to 90% show histological changes. The lesions of fibrocystic change, usually multiple and bilateral, are the most common palpable lesions sampled by FNA.
Histologic features include ductal dilatation, possibly resulting from periductal scarring, with subsequent formation of cysts, which are associated with apocrine metaplasia, ductal hyperplasia, fibrosis and chronic inflammation. FNA cytology is often poorly cellular because of the background fibrosis.
Cytological diagnostic features
- Low cellularity
- Flat, honeycomb epithelial sheets, with no loss of polarity and distinct cell borders
- Uniform small nuclei, low N/C ratio
- Bipolar naked nuclei
- Foamy cells and apocrine cells
- Fat and fibrous stromal tissue fragments
Apocrine cells can be arranged in flat sheets or as single cells, and show abundant granular cytoplasm and larger, more hyperchromatic nuclei with prominent nucleoli. Bipolar naked nuclei are often said to derive from myoepithelial cells, however they might also be derived from fibroblasts of the interlobular connective tissue. They are not specific of fibrocystic change, as they can be seen in other benign breast lesions (such as fibroadenoma).
Various degrees of epithelial proliferation occur in fibrocystic change, reflecting ductal hyperplasia, sclerosing adenosis, collagenous spherulosis, and atypical ductal hyperplasia. FNA smears of proliferative lesions show increased number of cohesive ductal cell groups and bipolar naked nuclei.
Cytological diagnostic features - proliferative fibrocystic change
- Moderate to high cellularity
- Cohesive epithelial groups with mild nuclear overlapping
- Myoepithelial cells within epithelial groups
- Bipolar naked nuclei in the background
- Apocrine and foamy cells
Aspirates of proliferative lesions can be a potential source of false-positive diagnoses of malignancy when the groups are hypercellular and show mild nuclear overlapping. The benign nature of the lesion should be suspected when a polymorphic population of cells is present, including apocrine, ductal and histiocytic cells, and especially when numerous bipolar naked nuclei are seen. FNA cytology is generally limited in its ability to subclassify proliferative breast lesions.
