Breast malignant
Breast cancer
WHO classification of breast tumors


Topic Completed: 14 January 2020

Minor changes: 22 April 2020

Copyright: 2012-2020, PathologyOutlines.com, Inc.

PubMed Search: WHO classification breast tumors [title]

Indu Agarwal, M.D.
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Cite this page: Agarwal I, Blanco L. WHO classification of breast tumors. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/breastmalignantwhoclassification.html. Accessed May 29th, 2020.
Definition / general
  • Updated 2019 WHO classification of tumors of the breast
    • Takes into account newer developments in the understanding of specific lesions
    • Emerging roles of stromal response and tumor microenvironment with specific attention to tumor infiltrating lymphocytes is emphasized
    • Carcinomas with medullary features have been subsumed into a combined morphological subset under the category of invasive carcinoma NST with basal like and medullary pattern
    • Following new entities have been recognized: "mucinous cysadenocarcinoma" and "tall cell carcinoma with reversed polarity"
    • Removal of well differentiated liposarcoma as a histologic criterion for malignancy in phyllodes tumor in the absence of additional supporting features
    • Updated information on molecular pathology, expression profiling and molecular classification of breast tumors, however, focus remains on morphologic classification
    • Some other notable changes:
      • Conversion of mitotic count from a common denominator of 10 high power fields to a defined area expressed as mm2
      • Importance of molecular pathology in aiding diagnosis is recognized
2019 WHO classification of tumors of the breast
  • Epithelial tumors

  • Invasive breast carcinoma
    • Infiltrating duct carcinoma (NOS), 8500/3
    • Oncocytic carcinoma, 8290/3
    • Lipid rich carcinoma, 8314/3
    • Glycogen rich carcinoma, 8315/3
    • Sebaceous carcinoma, 8410/3
    • Lobular carcinoma NOS, 8520/3
    • Tubular carcinoma, 8211/3
    • Cribriform carcinoma NOS, 8201/3
    • Mucinous adenocarcinoma, 8480/3
    • Mucinous cystadenocarcinoma NOS, 8480/3
    • Invasive micropapillary carcinoma of breast, 8507/3
    • Metaplastic carcinoma NOS, 8575/3

  • Rare and salivary gland type tumors
    • Secretory carcinoma, 8502/3
    • Acinar cell carcinoma, 8550/3
    • Mucoepidermoid carcinoma, 8430/3
    • Polymorphous adenocarcinoma, 8525/3
    • Adenoid cystic carcinoma, 8200/3
      • Classic adenoid cystic carcinoma
      • Solid basaloid adenoid cystic carcinoma
      • Adenoid cystic carcinoma with high grade transformation
    • Tall cell carcinoma with reversed polarity, 8509/3

  • Neuroendocrine neoplasms
    • Neuroendocrine tumor, NOS, 8240/3
    • Neuroendocrine tumor, grade 1, 8240/3
    • Neuroendocrine tumor, grade 2, 8249/3
    • Neuroendocrine carcinoma NOS, 8246/3
    • Neuroendocrine carcinoma, small cell, 8041/3
    • Neuroendocrine carcinoma, large cell, 8013/3

  • Epithelial - myoepithelial tumors
    • Pleomorphic adenoma, 8940/0
    • Adenomyoepithelioma NOS, 8983/0
    • Adenomyoepithelioma with carcinoma, 8983/3
    • Epithelial-myoepithelial carcinoma, 8562/3

  • Non invasive lobular neoplasia
    • Atypical lobular hyperplasia
    • Lobular carcinoma in situ NOS, 8520/2
      • Classic lobular carcinoma in situ
      • Florid lobular carcinoma in situ
    • Lobular carcinoma in situ, pleomorphic, 8519/2

  • Ductal carcinoma in situ (DCIS)
    • Ductal carcinoma, non infiltrating, NOS, 8500/2
      • DCIS of low nuclear grade
      • DCIS of intermediate nuclear grade
      • DCIS of high nuclear grade

  • Benign epithelial proliferations and precursors
    • Usual ductal hyperplasia
    • Columnar cell lesions including flat epithelial atypia
    • Atypical ductal hyperplasia

  • Adenosis and benign sclerosing lesions
    • Sclerosing adenosis
    • Apocrine adenoma, 8401/0
    • Microglandular adenosis
    • Radial scar / complex sclerosing lesion

  • Papillary neoplasms
    • Intraductal papilloma, 8503/0
    • Ductal carcinoma in situ, papillary, 8503/2
    • Encapsulated papillary carcinoma, 8504/2
    • Encapsulated papillary carcinoma with invasion, 8504/3
    • Solid papillary carcinoma in situ, 8509/2
    • Solid papillary carcinoma with invasion, 8509/3
    • Intraductal papillary adenocarcinoma with invasion, 8503/3

  • Adenomas
    • Tubular adenoma NOS, 8211/0
    • Lactating adenoma, 8204/0
    • Duct adenoma NOS, 8503/0

  • Mesenchymal tumors

  • Vascular tumors
    • Hemangioma NOS, 9120/0
      • Perilobular hemangioma
      • Venous hemangioma
      • Cavernous hemangioma
      • Capillary hemangioma
    • Angiomatosis
    • Atypical vascular lesion, 9126/0
      • Lymphatic atypical vascular lesion resembling lymphangioma
      • Vascular atypical vascular lesion resembling hemangioma
    • Postradiation angiosarcoma, 9120/3
      • Epithelioid angiosarcoma
    • Angiosarcoma, 9120/3
      • Epithelioid angiosarcoma

  • Fibroblastic and myofibroblastic tumors
    • Nodular fasciitis, 8828/0
    • Myofibroblastoma, 8825/0
    • Desmoid type fibromatosis, 8821/1
    • Inflammatory myofibroblastic tumor, 8825/1

  • Peripheral nerve sheath tumors
    • Schwannoma NOS, 9560/0
    • Neurofibroma NOS, 9540/0
    • Granular cell tumor NOS, 9580/0
    • Granular cell tumor, malignant, 9580/3

  • Smooth muscle tumors
    • Leiomyoma NOS, 8890/0
      • Cutaneous leiomyoma
      • Leiomyoma of the nipple and areola
    • Leiomyosarcoma NOS, 8890/3

  • Adipocytic tumors
    • Lipoma NOS, 8850/0
    • Angiolipoma NOS, 8861/0
    • Liposarcoma NOS, 8850/3

  • Other mesenchymal tumors and tumor-like conditions
    • Pseudoangiomatous stromal hyperplasia

  • Fibroepithelial tumors
    • Fibroadenoma NOS, 9010/0
    • Phyllodes tumor NOS, 9020/1
      • Periductal stromal tumor
    • Phyllodes tumor, benign, 9020/0
    • Phyllodes tumor, borderline, 9020/1
    • Phyllodes tumor, malignant, 9020/3
    • Hamartoma

  • Tumors of the nipple
    • Nipple adenoma, 8506/0
    • Syringoma NOS, 8407/0
    • Paget disease of the nipple, 8540/3

  • Malignant lymphoma
    • Diffuse large B cell lymphoma NOS, 9680/3
    • Burkitt lymphoma NOS/Acute leukemia, Burkitt type, 9687/3
      • Endemic Burkitt lymphoma
      • Sporadic Burkitt lymphoma
      • Immunodeficiency associated Burkitt lymphoma
    • Breast implant associated anaplastic large cell lymphoma, 9715/3
    • Mucosa associated lymphoid tissue lymphoma, 9699/3
    • Follicular lymphoma NOS, 9690/3

  • Metastatic tumors
  • Tumors of the male breast
    • Gynaecomastia
    • Carcinoma
      • Invasive carcinoma, 8500/3
      • In situ carcinoma, 8500/2
Microscopic (histologic) images

Contributed by Indu Agarwal M.D. and Mirna B. Podoll, M.D.
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DCIS

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LCIS, classic type

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Invasive ductal carcinoma

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Invasive lobular carcinoma


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Metastatic lobular carcinoma in lymph node

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Highlighted by AE1 / AE3

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Metaplastic carcinoma


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Encapsulated papillary carcinoma

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Adenoid cystic carcinoma

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