Summary

Background: Infiltrating ductal carcinoma and infiltrating lobular carcinoma account for more than 90% of all invasive breast cancer histological types. The rate of ILC[1] is reported to be increasing steadily in the United States and Europe.

Objectives: To describe the trend in the incidence of ILC in a large cohort of patients who underwent surgery in a single institution over an 18 year period.

Methods: Our comprehensive database of 2175 consecutive patients with invasive breast cancer diagnosed during the period 1992–2009 served for the analysis. Several potential factors associated with lobular carcinoma as compared with ductal carcinoma were evaluated.

Results: During this period, a 2.4-fold increase in the incidence of pure ILC was noted, from 4.6% in the years 1992–1994 to 10.9% in 2004–2006, followed by a modest decrease to 8.7% in 2007–2009. A significant association of lobular malignancies with external hormonal use was noted, including hormone replacement therapy exposure in patients diagnosed at age 50–64, and ovarian overstimulation during in vitro fertilization in those diagnosed at age 50 or less.  

Conclusions: Better diagnostic tools – such as the liberal use of ultrasound and magnetic resonance imaging – and more accurate pathological definition for ILC type appear to influence the changes in the incidence of ILC in the subgroups of invasive breast cancer.