Clinico-pathological characteristics of a distinct tumor phenotype: invasive lobular carcinoma with tubular elements (ILC-TE) in the WSG ADAPTcycle trial.

Background: Invasive lobular carcinoma with tubular elements (ILC-TE) is a recently identified variant of invasive lobular breast carcinoma (ILC). The histology of ILC-TE is defined by non-cohesive carcinoma cells mixed with cohesive tubular elements and complete loss of E-cadherin. Cell-cell adhesion is partially restored by switching from an E-cadherin-deficient to a P-cadherin-proficient status (EPS).

HER2-low status as a distinct breast cancer subtype: myth or truth? Analysis of the WSG trials WSG-ADAPT-HR+/HER2-, WSG-PlanB, and WSG-ADAPT-TN.

Background: New data show that not only HER2-overexpressing breast cancer (BC) tumors but also HER2-low tumors, classically considered as HER2-negative, respond to HER2-targeting antibody-drug-conjugates. Our objective was to analyze the prevalence of HER2-low BC in a pooled analysis of contemporary early BC trials and to evaluate its role as a prognostic factor in terms of survival in comparison to HER2-zero BC.

Methods: We evaluated 5598 patients with locally HR + /HER2- BC from the screening cohort of WSG-ADAPT-HR + /HER2-, 2592 patients with HR + /HER2- or HR-/HER2- from the adjuvant WSG-PlanB trial, and 336 patients from the WSG-ADAPT-TN trial.