Breast cancer classification

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Mirdula Sharma, MBBS [2] Soroush Seifirad, M.D.[3]

Breast cancer may be classified according to anatomy into 4 subtypes: ductal, lobular, sarcoma, and lymphoma. There are also other methods of classification such as classification based on gene expression, and classification based on hormone receptors present. In practice, a combination of all above mentioned classification is combined with the surgical characteristics of tumors and radiologic findings is being applied for patient management, treatment planning, and prognosis determination.

• Phyllodes tumor^[1]
• Mammary fibromatosis: 0.2% of all breast tumors 5
• Benign papillary lesions of the breast

• Papilloma

• Intraductal papilloma
• Solitary papilloma of breast
• Central solitary papilloma of breast
• Peripheral solitary papilloma of breast
• Multiple papillomata of breast

• Juvenile papillomatosis of breast

• Granular cell tumor of the breast

• Hormone receptor positive: either estrogen or progesterone receptors are present
• Hormone receptor negative: breast cancer cells do not have either estrogen or progesterone receptors
• HER2 positive: If excess copies of HER2 gene
• HER2 negative: If excess copies of HER2 gene are not present
• Triple positive: cancers that are ER-positive, PR-positive, and have too much HER2
• Triple negative: If the breast cancer cells don not have estrogen or progesterone receptors and don’t have too much HER2

• Luminal type: are estrogen receptor (ER)–positive

• Luminal A:

• Expression of luminal (low molecular weight) cytokeratins, high expression of hormone receptors and related genes
• 50% of invasive bresat cancer, ER/PR positive, HER2/neu negative
• Tubular carcinoma, Cribriform carcinoma, Low grade invasive ductal carcinoma, NOS, Classic lobularcarcinoma
• Response to endocrine therapy
• Variable response to chemotherapy
• Low grade,
• Grows slowly,
• Good prognosis (the best prognosis)

• Luminal B :

• Expression of luminal (low molecular weight) cytokeratins, moderate-low expression of hormone receptors and related genes
• 20% of invasive breast cancer, ER/PR positive, HER2/neu expression variable, higher proliferation than Luminal A, higher histologic grade than Luminal A
• Invasive ductal carcinoma, NOS Micropapillary carcinoma
• Response to endocrine therapy (tamoxifene and aromatase inhibitors) not as good as Luminal A
• Variable response to chemotherapy (better than Luminal A)
• Prognosis not as good as Luminal A
• Grows faster

• HER2/neu

• High expression of HER2/neu, low expression of ER and related genes
• 15% of invasive breast cancer, ER/PR negative, HER2/neu positive, high proliferation, diffuse TP53 mutation, high histologic grade and nodal positivity
• High grade invasive ductal carcinoma, NOS
• Response to trastuzumab (Herceptin)
• Response to chemotherapy with antracyclins
• Usually unfavorable prognosis

• Basal like

• High expression of basal epithelial genes and basal cytokeratins, low expression of ER and related genes, low expression of HER2/neu
• ~15% of invasive breast cancer, most ER/PR, HER2/neu negative (triple negative), high proliferation, diffuse TP53 mutation, BRCA1 dysfunction (germline, sporadi
• High grade invasive ductal carcinoma, NOS Metaplastic carcinoma, Medullary carcinoma
• No response to endocrine therapy or trastuzumab
• Sensitive to platinum group chemotherapy and PARP inhibitors
• Not all, but usually worse prognosis^[2]

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