Breast
General
WHO classification
Authors: Indu Agarwal, M.D., Luis Blanco, Jr., M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Last author update: 14 January 2020
Last staff update: 27 September 2023 (update in progress)
Copyright: 2012-2023, PathologyOutlines.com, Inc.
PubMed Search: WHO classification breast tumors
Table of Contents
Definition / general | Major updates | WHO (2019) | Microscopic (histologic) images | Additional references | Board review style question #1 | Board review style answer #1Cite this page: Agarwal I, Blanco L. WHO classification. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/breastmalignantwhoclassification.html. Accessed September 28th, 2023.
Definition / general
- WHO classification of tumors of the breast
- Currently on 5th edition, published in 2019
Major updates
- Carcinomas with medullary features have been subsumed into a combined morphological subset under the category of invasive carcinoma, no special type (NST) with basal like and medullary pattern
- The following new entities have been recognized
- Mucinous cystadenocarcinoma
- 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
- Conversion of mitotic count from a common denominator of 10 high power fields to a defined area expressed as mm2
WHO (2019)
- 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
- Ductal carcinoma, non infiltrating, NOS, 8500/2
- 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
- Hemangioma NOS, 9120/0
- 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
- Leiomyoma NOS, 8890/0
- 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
- Gynecomastia
- 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.
DCIS
LCIS, classic type
Invasive ductal carcinoma
Invasive lobular carcinoma
Metastatic lobular carcinoma in lymph node
Highlighted by AE1 / AE3
Metaplastic carcinoma
Encapsulated papillary carcinoma
Adenoid cystic carcinoma
Additional references
Board review style question #1
- Which of the following is true regarding breast tumor classification?
- Low grade atypical ductal proliferation of ≥ 3 mm should be called atypical ductal hyperplasia
- "Medullary carcinoma" is a distinct subtype and should be diagnosed as such
- "Solid papillary carcinoma" and "Encapsulated papillary carcinoma" are staged as invasive ductal carcinoma NOS, based on the largest dimension
- "Tall cell carcinoma with reversed polarity" and "Mucinous cystadenocarcinoma NOS" are two new entities
Board review style answer #1
D. "Tall cell carcinoma with reversed polarity" and "Mucinous cystadenocarcinoma NOS" are two new entities
Tall cell carcinoma with reversed polarity is a rare subtype of invasive breast carcinoma characterized by tall columnar cells with reversed nuclear polarity, arranged in solid and solid papillary patterns, and most commonly associated with IDH2p.Arg172 hotspot mutations. Mucinous cystadenocarcinoma of the breast is an invasive breast carcinoma characterized by cystic structures lined by tall columnar cells with abundant intracytoplasmic mucin, resembling pancreato-biliary or ovarian mucinous cystadenocarcinoma.
WHO Working Group recommends that "Encapsulated Papillary Carcinoma" and "Solid Papillary carcinoma" to be staged and managed as in situ lesions.
Tumors previously called as medullary carcinoma, atypical medullary carcinoma and invasive carcinoma with medullary features have been subsumed into a combined morphologic subset under the category of invasive carcinoma NST with basal-like and medullary pattern, regarding them as a part of a spectrum of tumor infiltrating lymphocytes rich breast carcinomas.
Atypical ductal hyperplasia represents a microfocal, low grade atypical proliferation not involving more than two complete duct spaces or equivalent i.e. ≤ 2 mm. Lesions of 3 mm dimension with complete duct spaces involvement should be called ductal carcinoma in situ (DCIS).
Comment Here
Reference: WHO classification - Breast
Tall cell carcinoma with reversed polarity is a rare subtype of invasive breast carcinoma characterized by tall columnar cells with reversed nuclear polarity, arranged in solid and solid papillary patterns, and most commonly associated with IDH2p.Arg172 hotspot mutations. Mucinous cystadenocarcinoma of the breast is an invasive breast carcinoma characterized by cystic structures lined by tall columnar cells with abundant intracytoplasmic mucin, resembling pancreato-biliary or ovarian mucinous cystadenocarcinoma.
WHO Working Group recommends that "Encapsulated Papillary Carcinoma" and "Solid Papillary carcinoma" to be staged and managed as in situ lesions.
Tumors previously called as medullary carcinoma, atypical medullary carcinoma and invasive carcinoma with medullary features have been subsumed into a combined morphologic subset under the category of invasive carcinoma NST with basal-like and medullary pattern, regarding them as a part of a spectrum of tumor infiltrating lymphocytes rich breast carcinomas.
Atypical ductal hyperplasia represents a microfocal, low grade atypical proliferation not involving more than two complete duct spaces or equivalent i.e. ≤ 2 mm. Lesions of 3 mm dimension with complete duct spaces involvement should be called ductal carcinoma in situ (DCIS).
Comment Here
Reference: WHO classification - Breast
