Terminal Duct Lobular Unit

Usual Ductal Hyperplasia

Lobular Carcinoma In Situ

Ductal Carcinoma In Situ

Invasive Ductal Carcinoma

Atypical Ductal Hyperplasia

Invasive Lobular Carcinoma

Collagenous Spherulosis

Fibroadenoma

Benign Phyllodes Tumor

Pseudoangiomatous Hyperplasia

Metaplastic Carcinoma

Myofibroblastoma

EPITHELIAL LESIONS

FIBROEPITHELIAL LESIONS

SPINDLED LESIONS

Atypical Lobular Hyperplasia

Sclerosing Adenosis

Microglandular Adenosis

Malignant Phyllodes Tumor

Radial Scar

Tubular Carcinoma

Cribriform Carcinoma

Medullary-Like Carcinoma

Intracystic Papillary Carcinoma

Intraductal Papilloma

Lactational Breast

Mucinous Carcinoma

Fibromatosis

Adenomyoepithelioma

Angiosarcoma

Nodular Fasciitis

Involves entire TDLU

Uniform cells

Mix of cell types

Express different cytokeratins

Small and uniform cells

E-cadherin negative

Myoepithelial markers

Cookie-cutter spaces

< 2-3 mm or only 1 duct

Cohesive cells

Secondary lumina

Rosette-like

Small and uniform cells

E-cadherin negative

Higher grade

Spaces

Normal sized lobules

Central lumina

Invasion

Single-filing

Adenoid Cystic Carcinoma

Small and uniform cells

E-cadherin negative

Higher grade

Dense, nodular material

2nd cell population:

CD117+ luminal cells

Invasive

Myoepithelial markers

Pink collagen-rich spherules

Circumscribed

Large cells

Vesicular nuclei

Stromal invasion

Mucinous component:

>90%: pure

75-90%: mixed

Angular tubular structures: >90%

Desmoplasia

Apical snouts

ER/PR+

Rounded tubes

Secretory material

Triple-negative

Lobular structure

Myoepithelial cells

Stellate, central scar

Hyperplasia, cysts

Atypia

No myoepithelial markers

VASCULAR LESIONS

Fibrovascular core

No myoepithelial component

Invasion into stroma

No myoepithelial layer

No tissue fragmentation at biopsy

More cellular

Stromal overgrowth

Stromal condensation

Leaf-like

More mitotic figures

>10 mitotic figures/10 HPF

Stromal > ductal overgrowth (no ducts at 4x)

Infiltration, necrosis, anaplasia

Well-circumscribed

Tissue-culture

Mucoid pools

Larger

Infiltrative

Diffuse

Uncircumscribed

Thick bands of collagen

Low-grade myofibroblastic sarcoma

Inflammatory myofibroblastic tumor

More heterogeneous

Less hyperchromasia

Less infiltrative

ALK+

Dense collagen

Infiltrative

Pleomorphic nuclei, mitoses

Some giant cells

Low mitotic activity

Atypia

Cytokeratin-positive

Cytokeratin-positive

May have malignant epithelial component

Background of Phyllodes

Cytokeratin-negative

Post-radiation Atypical Vascular Lesion

Slit-like

Flat fibroblastic cells

No necrosis/atypia

Hemorrhagic

Invasion into parenchyma

Hyperchromatic endothelial cells

CD31+, FVIII+

Atypical endothelial cells

Infiltrative

High-grade

More circumscribed

No extension to subcutis