Invasive lobular carcinoma (ILC) is the second most common subtype of breast cancer; ILC differs from invasive ductal carcinoma (IDC) both in clinicopathological characteristics and responsiveness to systemic therapy.
The ILC tumor genomic profiles differ from those of IDC.
Classical ILC is characterized by small, noncohesive cells that line up in a single-file pattern, making them very hard to see on a mammogram. Approximately 90% of ILCs lack E-cadherin protein expression.
ILC typically displays these features that are associated with a good prognosis:
- low to intermediate grade
- low Ki-67 expression
- positive estrogen receptor (ER) expression
- absence of HER2 protein overexpression or amplification
However, ILCs are more prone to spread to gastrointestinal, peritoneal and ovarian tissues than IDC.
How ILC differs from IDC
- Neoadjuvant research shows that patients with ILC do not benefit from chemotherapy as much as patients with IDC
- “Because the majority of patients with ILC have low-grade ER positive tumors, they are unlikely to derive significant benefit from either adjuvant or neoadjuvant chemotherapy”
- The adjuvant letrozole provides a greater benefit for patients diagnosed with ILC versus IDC.
In summary, “better tools are needed to identify the small fraction of [ILC] patients that might benefit from chemotherapy.
Romualdo Barroso-Sousa, Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA.Otto Metzger-Filho, Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, 450 Brookline Avenue, Yawkey 1238, Boston, MA 02215, USA.
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