Breast pathology

Diagram of the structure of breast. (CRUK/WC)

The breast is an important organ that pathologists see quite often because it is often afflicted by cancer. Before women started smoking in large numbers, it was a leading cause of cancer death in women.

Fortunately, breast cancer, in this day, has a relatively good prognosis if it is detected early.

Clinical

Clinical Presentations of Breast Pathology

• Abnormal/suspicious screening mammogram
  • Suspicious microcalcifications and/or suspicious mass.
  • Most common history on the specimen requisition
  • May be accompanied by a BI-RADS score.
• Nipple discharge.
• Pain.
• Breast lump/mass.
• New nipple inversion.
• Skin changes, e.g. peau d'orange.

Breast cancer screening

Breast cancer screening, for normal risk individuals, starts at age 50 in Canada. In the USA, breast screening starts at age 40.

Radiologic screening is less effective in younger individual as:

1. The breast is more dense and thus radiologically more difficult to interpret, and
2. The incidence of breast cancer is lower.

Breast radiology

Main article: Breast imaging reporting and data system

Specimens

Three major specimen types:

1. Core needle biopsy (CNB).
2. Lumpectomy.
3. Modified radical mastectomy.

Note:

• Breast cytopathology is dealt with in the breast cytopathology article. Breast cytology is almost extinct unless you happen to be in Australia where for reasons unknown, the art is still taken seriously. Breast cytology is not sensitive or specific enough to justify forgoing a CNB.

Core needle biopsy

Work-up of CNBs is dependent on the clinical abnormality:

1. Mass lesion - usu. obvious what is going on; typically 3 levels.
2. Calcifications - abnormality may be very small; typically 10 levels.

Note - if you have a high BI-RADS score on the biopsy requisition, and no correlating histologic findings, be sure to correlate with the specimen radiograph, consider leveling the specimen to exhaustion and/or note the lack of a correlating lesion on your report.

Lumpectomy

Lumpectomies are usually oriented with short and long suture; short is typically superior (aspect) and long is typically lateral (aspect).

Modified radical mastectomy

• Usually done with sentinel lymph node biopsy - as one cannot go back later to do this.

Where to start

Main articles: Short_power_list#Breast_pathology and Long_power_list#Breast_pathology

The following is a starting point for mentally framing routine breast pathology & some of the challenges in breast pathology:

The key to breast pathology is the myoepithelial cell.

• • A benign gland has two cell layers - myoepithelial and epithelial.
  • The luminal cell is epithelial
  • The basal cells is myoepithelial
    • The myoepithelial layer is hard to see at times.
    • IHC can aid in visualizing the myoepithelial layer.
    • The immunostains used in breast pathology for the myoepithelial layer include: CK5/6, SMA, p63 and calponin.

Questions to Ask

• Is it normal or close to normal?
  • Are you familiar with normal/altered but benign/physiologic changes in the breast?
  • Do the changes observed explain the biopsy (are you sure you are seeing the radiographic lesion)?
  • Have you found the microcalcifications?

• Is it a neoplastic but benign?
  • Are you familiar with the common benign breast neoplasms?
  • Do you know the morphologic criteria for a benign breast gland?
  • Do you know how to use IHC to confirm a benign process?

• Is it an in situ carcinoma?
  • Are you familiar with DCIS and LCIS and their variants?
  • Do you know the morphologic criteria for in situ carcinoma?
  • Do you know how to use ICH to confirm an in situ carcinoma?
  • Do you know how to report an in situ breast carcinoma?

• Is it invasive carcinoma?
  • Do you know the morphologic criteria for an invasive gland?
  • Do you know how to use IHC to confirm invasion?
  • Do you know the morphologic features of typical invasive breast carcinoma?
  • Do you know the subtypes?
  • Do you understand the implications of some of the medullary/medullary-like subtype (especially in a young patient)?
  • Do you know how to use IHC for prognostication?
  • Do you understand the implications of triple negativity?
  • Do you know how to report an invasive breast carcinoma?

• Is it something stromal/spindled?

Important Differential Diagnoses

Papillary Lesions

• Nipple adenoma.
• Intraductal papilloma.
• Papillary ductal carcinoma in situ.
• Intracystic papillary carcinoma.
• Intracystic papillary carcinoma with an invasive component.
• Invasive papillary carcinoma.

Basaloid Lesions

• Adenoid cystic carcinoma of the breast.
• Intracystic papillary breast carcinoma, solid variant.
• Invasive papillary breast carcinoma, solid variant.
• Medullary breast carcinoma.
• Medullary-like breast carcinoma.
  • Know when to start a discussion about BRCA mutations, triple negativity and the 'basal-like molecular phenotype'.

Spindle Cell Lesions

• Metaplastic breast carcinoma.
• Treated breast carcinoma.
• Mammary myofibroblastoma.
• Phyllodes Tumour - stromal component.
• Desmoid fibromatosis.
• Nodular fasciitis.

Additional resources

• Breast Pathology Info [1]
• Digital Atlas of Breast Pathology [2]
• Pathology Outlines - Breast Nonmalignant [3]
• Pathology Outlines - Breast Malignant [4]
• WebPathology - Breast [5]

Normal breast

Resting breast

• Glands -- normally has two cell layers (like the prostate).
  • Myoepithelial cells
    • Frequently spindle-like, often hard to see.
  • Secretory cells.
• Stroma:
  • Not cellular.
  • Not myxoid.

May be present:

• Calcification:
  • Purple globs (with concentric rings) on H&E = calcium phosphate.
    • Q. How to remember? A. Purple = Phosphate.
  • Calcium oxalate visible with (light) polarization - not associated with malignancy.
  • Often in the lumen of a gland, may be in the stroma.
  • Calcific material typically has a well-demarcated border +/- "sharp corners".
  • Radiologists can pick-up calcs (calcifications) that are approximately 100 micrometers; if "calcs" is on the requisition one needs to find calcs this size.
    • The large calcs seen on radiology are approximately 1/5 - 1/6 the size of a HPF, if the field of view (FOV) is ~0.55 mm (as is the case with 22 mm-10x eye pieces and a 40x objective).

Notes:

• The architecture is more important than the cytologic features in the diagnosis of malignancy in the breast; low grade tumours have distorted architecture but normal/near normal cytology.

Image

• Breast with calcifications (breastpathology.info).
• Resting breast tissue (wjso.com).

Lactational changes

• AKA secretory change, AKA lactational adenoma, AKA lactating adenoma

General

• Lactational adenoma generally arises in during or in the few weeks after pregnancy.
• May be present focally in non-pregnant females.
• "Lactational adenoma"- circumscribed mass displacing the normal breast architecture (hyperplasia plus functional/physiologic change)
• "Lactational change"- normal breast tissue architecture preserved (functional/physiologic change).

ASIDE:

• Some believe lactational change and secretory change aren't the same...
  • Lactational change = only in lactation.
  • Secretory change = other times.
• This hair splitting is clinically irrelevant-- both are benign. Also, experts use the terms interchangeably.

Microscopic

Features:

• Glands dilated.
• Increased number of lobules.
  • Relative decrease in intralobular and extralobular stroma.
• Luminal cells enlarged.
  • Vacuolated cytoplasm.
  • Hobnail morphology - hang into the lumen.
• Myoepithelial cells indistinct - after second trimester.
• Lactational "adenoma" may undergo infarction - Imagine what an infarcted lactational adenoma could look like in a FNA specimen!

DDx:

• Secretory carcinoma of the breast.

Images

• 

  Lactational change - low mag. (WC/Nephron)

• 

  Lactational change - high mag. (WC/Nephron)

• 

  Breast - Lactational Change - medium power (SKB)

• 

  Breast - Lactational Change - high power (SKB)

• 

  Breast - Lactational adenoma - medium power (SKB)

• 

  Breast - Lactational adenoma - high power (SKB)

• 

  Breast - Lactational adenoma - low power (SKB)

• 

  Breast - Lactational adenoma - low power (SKB)

• 

  Lactational adenoma - high power - in this example, the epithelium is flattened with clear bubbly cytoplasm (SKB)

• 

  Breast - Lactational adenoma - high power - shows snouting and decapitation secretion. (SKB)

www:

• Lactational changes (gfmer.ch).
• Lactational changes in an angiosarcoma of the breast (webpathology.com).
• Lactating breast (uwa.edu.au).

Major Pathologic Patterns

General classification

Breast pathology

Stromal pathology

Miscellaneous

Glandular pathology

Myxoid

Long slit-like spaces

Simple epithelium

Dilated

Cellular lesions

Fibroadenoma

Malignant features

Benign features

Tubular carcinoma

FEA, FCC, CCC

FEHUT, Neoplastic, Malignant

Malignant phyllodes

Benign phyllodes

Notes:

• The challenges in breast pathology are in: the Simple epithelium category and the Cellular lesions category.
• Neoplastic includes: ADH and LDH.
• Malignant includes: DCIS, LCIS, ductal carcinoma (DC) and lobular carcinoma (LC), some papillary lesions.
• Lobular carcinoma (a pitfall) may appear to be a stromal problem, i.e. the stroma looks too cellular.
• Miscellaneous includes rare tumours of the breast that do not fit into another category, i.e. metastases, lymphomas, melanoma, sarcomas. Skin-related pathology is dealt within the dermatologic neoplasms article. Paget disease of the breast, which may be seen in the context of malignant breast lesions, is discussed in its own article.

Cellular lesions

Cellular lesions (Glandular)

Equal spacing, punched-out

Streaming, periph. slit-like spaces.

Discohesive cells, expanded gl.

Single cells or single file

Fibrovascular cores

Ductal lesion

FEHUT

Lobular lesion

Lobular carcinoma

Papillary lesions

Two cell layers

One cell layer

<50% of gl.

>50% of gl.

Ductal non-inv. neoplasm

Ductal carcinoma

ALH

LCIS

Large extent

Small extent

DCIS

ADH

Notes:

• The largest challenge is: differentiating between the first two categories on level 2, i.e. equal spacing' vs. streaming.
• The fibrovascular cores must arise from a tuft, i.e. if they are arising directly from the wall of glands only it is likely papillary DCIS.

Papillary lesions

Papillary lesions

Myoepithelial cells present

Myoepithelial cells absent

Unremarkable papillae

Atypia or arch. abnorm. or cellular proliferation

Neoplastic cells present

Benign intraductal papilloma

High grade atypia

Low grade atypia or abnorm. arch.

Only cellular proliferation

Intracystic (encapsulated) papillary ca.

DCIS in papilloma

FEHUT in papilloma

>3 mm extent

<3 mm extent

DCIS in papilloma

ADH in papilloma

Notes:

• Adapted from Mulligan & O'Malley.
• The most important decision is the first one: myoepithelial cells present vs. absent.
• abnorm. arch. = abnormal architecture present.
• DCIS = ductal carcinoma in situ.
• FEHUT = florid epithelial hyperplasia of the usual type.
• extent refers to the size of the abnormal cell population within the papillary lesion.

Malignant lesions

Non-invasive breast cancer

Main article: Non-invasive breast cancer

This includes the in situ lesions - DCIS and LCIS.

Invasive breast cancer

Main article: Invasive breast cancer

This is includes descriptions of the usual types... and the not so common ones.

Common benign lesions

The breast has lots of benign things. Unlike the prostate, the where benign is called benign, everything has a name. It is more common among breast pathologists to sign-out things like: apocrine metaplasia (benign), columnar cell change (benign), and florid epithelial hyperplasia of the usual type (FEHUT) - instead of - benign breast tissue.

Mild epithelial hyperplasia

General

• No increased risk of malignancy.
  • Often not reported - as it has no clinical signficance.
• Has to be separated from moderate epithelial hyperplasia / florid epithelial hyperplasia.

Microscopic

Features:

• Breast glands with three or four cell layers above the basement membrane.
• Variable cells.

Note:

• No nuclear atypia.

DDx:

• Flat epithelial atypia.
• Moderate epithelial hyperplasia / florid epithelial hyperplasia.
• Atypical ductal hyperplasia.

Apocrine metaplasia

Main article: Apocrine metaplasia of the breast

Duct ectasia

• Dilation of large ducts secondary to luminal obstruction by inspissated secretions
• Presentation
  • ~age 40-50, possibly with cheesy nipple discharge
• Pathology
  • Duct lumen dilated and containing foamy macrophages
  • Necrosis/shedding of epithelium
  • If duct rupture: chronic and granulomatous inflammation of periductal region
  • Fibrotic thickening of duct wall

• 

  Breast - Duct Ectasia - low power (SKB)

• 

  Breast - Duct Ectasia - low power (SKB)

• 

  Breast - Duct Ectasia - medium power (SKB)

Fibrocystic change

Main article: Breast fibrocystic changes

• AKA fibrocystic changes (abbreviated FCC).

Columnar cell change

Main article: Columnar cell change of the breast

Gynecomastoid hyperplasia

• AKA gynecomastia.

Main article: Gynecomastoid hyperplasia

Breast prostheses

Main article: Breast prostheses

Lesions with increased risk of malignancy

Florid epithelial hyperplasia

• AKA florid epithelial hyperplasia of the usual type, abbreviated FEHUT.
• AKA epithelial hyperplasia - term should be avoid as it could lead to confusion with mild epithelial hyperplasia.
• AKA usual ductal hyperplasia, abbreviated UDH.

Main article: Florid epithelial hyperplasia

Sclerosing adenosis

Main article: Sclerosing adenosis of the breast

Flat epithelial atypia

• Abbreviated FEA.

Main article: Flat epithelial atypia

Complex sclerosing lesion

• AKA radial scar.

Main article: Complex sclerosing lesion

Stromal lesions

This section (below) covers stromal lesions of the breast, which vary from benign to malignant. The most common is (the benign) fibroadenoma.

Non-breast stroma stromal lesions are covered in the soft tissue lesions article. Angiosarcoma (dealt with in the vascular tumours article) is the most common (non-breast stroma) sarcoma of the breast, and classically arises after treatment for a breast carcinoma.

Fibroadenoma

Main article: Fibroadenoma

Phyllodes tumour

• Previously cystosarcoma phyllodes.

Main article: Phyllodes tumour

Pseudoangiomatous stromal hyperplasia

• Abbreviated PASH.
• AKA nodular myofibroblastic stromal hyperplasia of the mammary gland.

Main article: Pseudoangiomatous stromal hyperplasia

Weird stuff

Like in all niches of pathology... there is weird stuff.

Mammary hamartoma

• AKA breast hamartoma.

Main article: Mammary hamartoma

Collagenous spherulosis

• AKA mucinous spherulosis, AKA spherulosis.

Main article: Collagenous spherulosis

Nipple adenoma

• AKA nipple duct adenoma.
• AKA nipple adenoma of breast.
• AKA adenoma of the nipple.
• AKA florid papillomatosis of the nipple.

Main article: Nipple adenoma

Intraductal papilloma

• AKA papilloma.

Main article: Intraductal papilloma of the breast

Lymphocytic mastitis

• If the individual has diabetes mellitus it is diabetic mastopathy.

Main article: Lymphocytic mastitis

Microglandular adenosis

Not to be confused with microglandular hyperplasia.

• Abbreviated MGA.

Main article: Microglandular adenosis

Adenomyoepithelioma

Main article: Adenomyoepithelioma

Mammary myofibroblastoma

• AKA breast myofibroblastoma.
• AKA myofibroblastoma of the breast.

Main article: Mammary myofibroblastoma

Squamous metaplasia of lactiferous ducts

• Abbreviated SMOLD.

Main article: Squamous metaplasia of lactiferous ducts

Granular cell tumour of the breast

Main article: Granular cell tumour

General

• Uncommon.

Gross

• May be a spiculated mass and thus mimic malignancy radiologically.

Microscopic

See granular cell tumour.

DDx:

• Invasive lobular carcinoma.

See also

• Breast cytopathology.
• Salivary gland.
• Invasive breast cancer.
• Non-invasive breast cancer.

External links

• A collection of breast pathology cases (breastpathology.info).
• Breast pathology (webpathology.com).