Types of breast cancer and prognosis
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Breast Cancer Types: Molecular and Histological Subtypes
Breast cancer is a highly diverse disease, classified by both molecular markers and histological (tissue-based) features. The main molecular subtypes are based on the presence or absence of hormone receptors (estrogen and progesterone) and the HER2 protein. These subtypes include:
- HRc(+)/HER2(−) (Hormone receptor positive, HER2 negative)
- HRc(+)/HER2(+) (Hormone receptor positive, HER2 positive)
- HRc(−)/HER2(+) (Hormone receptor negative, HER2 positive)
- HRc(−)/HER2(−) (Triple-negative: lacks both hormone receptors and HER2) Hwang2018Łukasiewicz2021Lobbezoo2013
Histologically, breast cancers are further divided into types such as ductal carcinoma (the most common), lobular carcinoma, mucinous, tubular, medullary, metaplastic, micropapillary, papillary, cribriform, and several rare subtypes Kim2020Han2020Bae2019+1 MORE.
Prognosis by Molecular Subtype
The prognosis of breast cancer varies significantly by molecular subtype:
- HRc(+)/HER2(−): This is the most common subtype and has the best prognosis, with a 5-year breast cancer–specific survival (BCSS) rate of 95.5% .
- HRc(+)/HER2(+): Also associated with a favorable prognosis, with a 5-year BCSS of 94.1% Hwang2018Lobbezoo2013.
- HRc(−)/HER2(+): Intermediate prognosis, with a 5-year BCSS of 89.3% .
- Triple-negative (HRc(−)/HER2(−)): This subtype has the worst prognosis, with a 5-year BCSS of 83.1% and the shortest survival in metastatic cases (median 8.8 months) Hwang2018Lobbezoo2013.
These molecular subtypes are independent prognostic factors, meaning they predict outcomes regardless of other patient characteristics Hwang2018Łukasiewicz2021Lobbezoo2013.
Prognosis by Histological Subtype
Histological subtypes also influence prognosis:
- Special histological types (such as mucinous, tubular, papillary, cribriform, and some forms of medullary carcinoma) often have a better prognosis than the common invasive carcinoma of no special type (NST) Kim2020Han2020Bae2019+1 MORE.
- Metaplastic carcinoma is an exception among special types, showing a worse prognosis compared to NST Kim2020Han2020Bae2019.
- Mucinous breast cancer is rare but generally has a better long-term prognosis and less aggressive behavior than NST .
- Triple-negative breast cancers (TNBCs) are usually aggressive, but some rare histological subtypes of TNBC (such as adenoid cystic carcinoma, low-grade adenosquamous carcinoma, and others) have a favorable prognosis and may not require aggressive chemotherapy .
Factors Affecting Prognosis
In addition to subtype, other important factors influencing prognosis include tumor size, lymph node involvement, tumor grade, and the presence of metastases. High-grade tumors, large size, and extensive lymph node involvement are associated with poorer outcomes Page1991Schnitt2010.
Conclusion
Breast cancer prognosis is strongly influenced by both molecular and histological subtypes. Hormone receptor–positive and HER2-positive cancers generally have the best outcomes, while triple-negative and metaplastic subtypes are associated with poorer survival. However, some rare histological subtypes, even within the triple-negative group, can have favorable prognoses. Understanding these differences is crucial for guiding treatment and predicting outcomes.
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