Abstract P1-01-07: Clinical and histological characteristics of peritoneal metastases of invasive lobular breast cancer
Authors: Karsten MM , Ingold-Heppner B , Oesterreich S , Sander S , Machleidt A , von Waldenfels G , Denkert C , Blohmer JU 
Published: February 2018

Introduction: In previously reported autopsy series, peritoneal metastases have been detected in up to 40% of patients with invasive lobular breast cancer (ILC). Despite modern diagnostic techniques such as high-resolution ultrasound, it remains a challenge to differentiate ovarian cancer from metastatic breast cancer with peritoneal manifestation before or during surgery. 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. Imaging and surgical reports of these 58 patients with ILC intraperitoneal metastases were reviewed. Results: The majority (84.7%) of primary breast cancers consisted of 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&lt;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 stable with no difference in 53.3% and a rise in the metastatic site in only 26.7% (p= 0.715). Median age of all patients with primary breast cancer was 60 years (10%-90%: 41-75). There was a significant difference in age at diagnosis of metastasis between patients with (50.5 years) and without peritoneal metastases (59 years) (p= 0.002). Median time to development of peritoneal metastases for all patients was 48.5 months (10%-90%: 0-191.7), for ILC 44 months (0-198.2) and for Non-ILC 56.5 months (6.7-206.4) (p= 0.487). Median survival time for patients with ILC and peritoneal metastases was 56 months, for Non-ILC 53 months (p=0.759). 33 of 58 patients had radiologic evidence of disease, 26 with ILC and 7 with Non-ILC. An ovarian mass was detected by imaging in 15/26 patients with ILC and 4/7 patients with non-ILC. Ascites and diffuse peritoneal metastases were seen in 18/26 patients with detectable ILC and in 4/7 patients with Non-ILC.

Conclusion: This is the first comprehensive analysis of clinical and pathological characteristics of peritoneal metastases showing ILC is more frequent than other histologic subtypes. Patients with peritoneal metastasis are significantly younger (median 50.5y.) than patients without. The clinical signs are similar to those of ovarian cancer except and therefore the diagnosis of metastatic ILC must be taken into consideration as a differential diagnosis.

Citation Format: Karsten MM, Ingold-Heppner B, Oesterreich S, Sander S, Machleidt A, von Waldenfels G, Denkert C, Blohmer JU. Clinical and histological characteristics of peritoneal metastases of invasive lobular breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-01-07.