Clinical and histological characteristics of peritoneal metastases of ILC

Introduction:

The goal of this analysis was to determine typical clinical and immunohistological features of peritoneal metastasis of ILC. Specifically, we asked the question whether there are predictive factors in primary breast cancer associated with subsequent development of peritoneal metastasis.

Patients and methods:

We identified 58 patients with ovarian metastases in the Charité cancer register (4,792 breast cancer patients from 2003 to 2015). We looked for clinical and pathological differences between breast cancer patients with (N = 58) and without (N = 4734) peritoneal metastases and between ILC and non-ILC breast cancer subtypes.

Results:

The majority (84.7%) of primary breast cancers consisted of histological subtypes other than ILC and only 15.3% were histologically characterized as ILC. In contrast, 63.6% of patients with peritoneal metastases had histologically proven ILC in the metastatic tissue. Other subtypes where found in the 36.4% of the metastatic tissue (p < 0.001). The Odds ratio for peritoneal metastases for ILC was 2.35 (95% CI 1.655 – 3.332) and for Non-ILC 0.23 (0.185 – 0.284). There were no significant differences in receptor status between primary and peritoneal metastatic ILC. Comparing ER/PR expressions levels on primary tumor versus metastasis, while statistically not significant (p = 0.805), showed a rise in ER expression in 42.95% in the metastatic tissue while PR expression remained mostly stable with no difference in 53.3% and a rise in the metastatic site in only 26.7% (p = 0.715).

Conclusion:

This is the first comprehensive analysis of clinical and pathological characteristics of peritoneal metastases showing ILC is more frequent than other histologic subtypes.