[Basal-like breast cancer: a review]

Area of Science:

• Oncology
• Pathology
• Molecular Biology

Background:

• Basal phenotype breast cancers are recognized through molecular profiling and linked to adverse clinical outcomes.
• These aggressive tumors often lack key biomarkers like estrogen receptor, progesterone receptor, and HER2.

Purpose of the Study:

• To review the morphological features of basal phenotype breast cancers.
• To detail the immunohistochemical profiling used to characterize these tumors.
• To explore the prognostic implications of different basal subtypes.

Main Methods:

• Morphological assessment of tumor characteristics.
• Immunohistochemistry (IHC) for basal cytokeratins (CK5/6, CK14), myoepithelial markers (p63, smooth muscle actin), and HER1.
• Analysis of hormone receptor (ER, PR) and HER2 expression status.

Main Results:

• Basal phenotype breast cancers are characterized by the absence of hormone receptors and HER2, alongside expression of basal cytokeratins and myoepithelial markers.
• This phenotype can occur across various histological types of breast cancer.
• Three subtypes (pure basal, basal/myoepithelial, myoepithelial) were identified, with pure basal and basal/myoepithelial subtypes exhibiting a poor prognosis.

Conclusions:

• Immunohistochemistry is crucial for identifying and classifying basal phenotype breast cancers.
• Subtyping based on protein expression and prognosis is essential for understanding basal breast cancer heterogeneity.
• The identification of distinct subtypes highlights the need for tailored therapeutic strategies for basal breast cancers.