1.2.2 Pathological Classification
International histological classification of breast cancer by WHO（4th edition）［19-20］
Epithelial Tumours
1.Microinvasive carcinoma
2.Invasive breast carcinoma
2.1 Invasive carcinoma of no special type（NST）
（1）Pleomorphic carcinoma
（2）Carcinoma with osteoclast-like stromal giant cell
（3）Carcinoma with choriocarcinomatous features
（4）Carcinoma with melanotic features
2.2 Invasive lobular carcinoma
（1）Classic lobular carcinoma
（2）Solid lobular carcinoma
（3）Alveolar lobular carcinoma
（4）Pleomorphic lobular carcinoma
（5）Tubulolobular carcinoma
（6）Mixed lobular carcinoma
2.3 Tubular carcinoma
2.4 Cribriform carcinoma
2.5 Mucinous carcinoma
2.6 Carcinoma with medullary features
（1）Medullary carcinoma
（2）Atypical medullary carcinoma
（3）Invasive carcinoma NST with medullary features
2.7 Carcinoma with apocrine differentiation
2.8 Carcinoma with signet-ring-cell differentiation
2.9 Invasive micropapillary carcinoma
2.10 Metaplastic carcinoma（of no special type）
（1）Low-grade adenosquamous carcinoma
（2）Fibromatosis-like metaplastic carcinoma
（3）Squamous cell carcinoma
（4）Spindle cell carcinoma
（5）Metaplastic carcinoma with mesenchymal differentiation
①Chondroid differentiation
②Osseous differentiation
③Other types of mesenchymal differentiation
（6）Mixed metaplastic carcinoma
（7）Myoepithelial carcinoma
2.11 Rate types and variants of invasive carcinoma
（1）Carcinoma with neuroendocrine features
①Neuroendocrine tumour，well-differentiated
②Neuroendocrine carcinoma，poorly differentiated（small cell carcinoma）
③Carcinoma with neuroendocrine differentiation
（2）Secretory carcinoma
（3）Invasive papillary carcinoma
（4）Acinic cell carcinoma
（5）Mucoepidermoid carcinoma
（6）Polynorphous carcinoma
（7）Oncocytic carcinoma
（8）Lipid-rich carcinoma
（9）Glycogen-rich clear cell carcinoma
（10）Sebaceous carcinoma
（11）Salivary gland/skin adnexal type tumours of breast
①Cylindroma
②Clear cell hidradenoma
3.Epithelial-myoepithelial tumours
3.1 Pleomorphic adenoma
3.2 Adenomyoepithelioma（AME）
3.3 Adenomyoepithelioma with carcinoma
3.4 Adenoid cystic carcinoma
4.Precursor lesions
4.1 Ductal carcinoma in situ（DCIS）
（1）DCIS of low nuclear grade
（2）DCIS of intermediate nuclear grade
（3）DCIS of high nuclear grade
4.2 Lobular neoplasia
（1）Lobular carcinoma in situ
①Classic lobular carcinoma in situ
②Pleomorphic lobular carcinoma in situ
（2）Atypical lobular hyperplasia
5.Intraductal proliferative lesions
5.1 Usual ductal hyperplasia（UDH）
5.2 Columnar cell lesions including flat epithelial atypia
5.3 Columnar cell change and hyperplasia(https://www.daowen.com)
5.4 Flat epithelial atypia
5.5 Atypical ductal hyperplasia（ADH）
6.Intraductal papillary lesions
6.1 Intraductal papilloma
（1）Intraductal papilloma with atypical hyperplasia
（2）Intraductal papilloma with ductal carcinoma in situ
（3）Intraductal papilloma with lobular carcinoma in situ
6.2 Intraductal papillary carcinoma
6.3 Encapsulated papillary carcinoma
（1）Encapsulated papillary carcinoma with inwasion
6.4 Solid papillary carcinoma
（1）Solid papillary carcinoma in situ
（2）Solid papillary carcinoma with invasion
7.Benign epithelial proliferations
7.1 Sclerosing adenosis
7.2 Apocrine adenosis
7.3 Microglandular adenosis
7.4 Radical scar/complex sclerosing lesions
7.5 Adenomas
（1）Tubular adenoma
（2）Lactating adenoma
（3）Apocrine adenoma
（4）Ductal adenoma
Mesenchymal tumours
1.Nodular fasciitis
2.Myofibroblastoma
3.Desmoid-type fibromatosis
4.Inflammatory myofibroblastic tumour
5.Benign vascular lesions
5.1 Haemangioma
5.2 Angiomatosis
5.3 Atypical vascular lesions
6.Pseudoangiomalous stromal hyperplasia
7.Granular cell tumours
8.Benign peripheral nerve—sheath tumours
8.1 Neurofibroma
8.2 Schwannoma
9.Angiolipoma
9.1 Angiolipoma
10.Liposarcoma
11.Angiosarcoma
12.Rhabdomyosarcoma
13.Osteosarcoma
14.Leiomyoma
15.Leiomyosarcoma
Fibroepithelial tumours
1.Fibroadenoma
2.Phyllodes tumor
2.1 Benign
2.2 Boundary
2.3 Malignant
2.4 Periductal stromal tumour，low grade
3.Hamartoma
Tumours of the nipple
1.Nipple adenoma
2.Syringomatous tumour
3.Paget disease of the nipple
Malignant lymphoma
1.Diffuse large B-cell lymphoma
2.Burkitt lymphoma
3.T cell lymphoma
3.1 Anaplastic large cell lymphoma，ALK-negative
3.2 Extranodal marginal-zone B-cell lymphoma of MALT type
4.Follicular lymphoma
Metastatic tumours
Tumours of the male breast
1.Gynaecomastia
2.Carcinoma
2.1 Invasive carcinoma
2.2 Carcinoma in situ
Clinical patterns
1.Inflammatory carcinoma
2.Bilateral breast carcinoma