Classification
Triple-negative breast cancers are sometimes classified into "basal-type" and other cancers; however, there is no standard classification scheme. Basal type cancers are frequently defined by cytokeratin 5/6 and EGFR staining. However no clear criteria or cutoff values have been standardized yet. About 75% of basal-type breast cancers are triple negative.
Some TNBC overexpresses epidermal growth factor receptor (EGFR). Some TNBC over expresses transmembrane glycoprotein NMB (GPNMB).
On histologic examination triple negative breast tumors mostly fall into the categories secretory carcinoma or adenoid cystic types (both considered less aggressive), medullary cancers and grade 3 invasive ductal carcinomas with no specific subtype, and highly aggressive metastatic cancers. Medullary TNBC in younger women are frequently BRCA1-related.
Rare forms of triple negative breast cancer are apocrine and squamous carcinoma.
Inflammatory breast cancer is also frequently triple negative.
Many proteins such as Caveolin 1/2, Survivin are researched as possible classification/prognostic factors.
Read more about this topic: Triple-negative Breast Cancer