Breast cytopathology

Breast cytopathology is a relatively small part of cytopathology, as core biopsies are more in style.

This article deals only with breast cytopathology. An introduction to cytopathology is in the cytopathology article.

Overview

Common indications

1. FNA done for a clinically benign lesion - unusual to find malignancy.
2. FNA of a satellite lesion to assess extent of a presumed cancer; done together with a core biopsy of another site.

Pitfalls

False negative:

• Lobular carcinoma - often single cells (may be in "chains"/"single file"), slightly hypercellular, cells appear bland/normal cytologically (if not carefully examined).

Malignancy - the short version

• If the cells are not dissociated... cancer is not likely.
• If there are stripped bipolar nuclei (these represent normal stromal cell) - cannot call overt malignancy.

Normal

Features:

• Sheets of flat cells.
• Usu. no nucleoli.
• Stripped bipolar (elliptical) nuclei.
• +/-Adipose tissue:
  • Peripheral nucleus.
  • One large vacuole.

Notes:

• Adipose tissue may represent a lipoma.

Breast cytopathology in a table

The common entities in breast cytopathology and their features:

Entity	Key feature	Architecture	Cells	Images
Normal	Flat sheets of cells, stripped bipolar nuclei	Flat sheets	Uniform size, lack nucleolus
Fibroepithelial lesion (fibroadenoma, phyllodes)	Clusters of cells with staghorn shape (jagged edge), bare bipolar nuclei	Flat sheets & fluffy paucicellular (fibrous) tissue	Mixed pop. in cluster; nuclei: oval/spindle (myoepi.) and round (epi.).	Fibroadenoma - FNA (WC), Fibroadenoma FNA - Diff-Quik (WC)
Fibrocystic change	Macrophages	May have flat sheets of cells	Oncocytic change (apocrine change) common, histocytes (foamy cytoplasm), nucleoli, large NCR	Oncocytes in FCC (WC)
Papillary neoplasm	Stalks (fibrovascular cores)	Sheets, usu. flat?	Variable size, nucleolus	Papillary neoplasm (WC)
Ductal carcinoma	Nuclear atypia, lack of stripped bipolar nuclei	3-D clusters	Nuclear size variation, membrane irreg., nucleoli (prominent) - every cell, cell size var.	Ductal carcinoma - animation showing 3-D nature (WC)

Fat necrosis

Features:

• Dying adipocytes - pink low density whispy poorly demarcated blobs, lack nucleus.
  • Healthy adipocytes - large cells, clear cytoplasm.
• Foamy macrophages - adjacent to fat.
  • Abundant cytoplasm - with granular crap inside.
  • Oval nucleus with small nucleolus.

Adenocarcinoma

• By convention one usually calls everything ductal carcinoma.

Cytopathology

Five features:

1. Cellular size variation.
2. Nuclear size variation.
   • May be marked adjacent cells different by factor of 2.
   • Typically not marked - often ~1.5.
3. Nucleoli.
   • Should be in every cell.
   • Multiple suggestive of malignant.
4. Irregular chromatin pattern.
5. Lack of singular bipolar nuclei (in the background), key negative.

Other features:

• 3-D clusters - strong indicator.
• Cytoplasmic vacuoles - considered a classic finding.

Notes:

• Typically single cells present.
  • Exceptions are tubular carcinoma and colloid carcinoma; these have cells found in clusters or tubules/glands.
• Intracytoplasmic "lumens"/inclusions (think lobular carcinoma).

Images:

• Ductal carcinoma - animation showing 3-D nature (WC).
• Ductal carcinoma (WC).

Fibroadenoma

Features:

• Flat sheet of cells with mixed population - key feature:
  • Cells with round nuclei (epithelium).
  • Cells with oval nuclei (myoepithelium).
• Stromal fragments:
  • Spindle cells.
  • Fluffy appearance - relatively paucicellular.

Images:

• Fibroadenoma - FNA (WC).
• Fibroadenoma FNA - Diff-Quik (WC).

Apocrine metaplasia/fibrocystic changes

Features:

• Architecture - pretty much anything (flat, single, papillary, clusters, sheets).
• Oncocytic change:
  • Finely granular cytoplasm - key feature.
  • Well-defined cell borders.
  • Nuclei round typically with one nucleolus (occasionally several nucleoli).
• Macrophages (foamy) - key feature.
  • Vacuolated cytoplasm + round/oval nuclei.

Image:

• Oncocytes in FCC (WC).

Paget's disease

Features:

• Usually large cells with:
  • Nuclear atypia and nucleolus.
  • Abundant bubby (vacuolated) cytoplasm.
• Malignant cell may have "cell-in-cell" arrangement.

Papillary neoplasm

Features:

• Fibrovascular core - key feature.

Image:

• Papillary neoplasm (WC).

See also

• Cytopathology.
• Basics.
• Breast.
• Breast cancer.