title: Specific sites of metastases in invasive lobular carcinoma: a retrospective cohort study of metastatic breast cancer.
abstract: BACKGROUND
  Invasive lobular carcinoma (ILC) is known to be the second most common histological type following invasive ductal carcinoma (IDC). Definitive clinical features of ILC are controversial.
  
  
  METHODS
  We retrospectively analyzed a cohort of 330 patients with metastatic breast cancer, 303 of IDC, 19 of ILC, and 8 of others. We compared the patient age and tumor-node-metastasis factors, disease-free survival (DFS), estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor 2 (HER2) expression at the primary site between ILC and IDC. We then selected the patients in the ER+or PR+/HER2-subtype specifically and compared sites of recurrence, and the survival curve starting from the point of development of metastatic disease.
  
  
  RESULTS
  The clinical stage was significantly higher in the ILC patients than in the IDC (p = 0.001). The mean (±SD) of DFS for the ILC and IDC patients was 2.6 ± 0.6 and 2.4 ± 0.3 years, respectively, with no significant difference (p = 0.18). However, the hormone receptor status was same between both groups; the rate of HER2 positivity was significantly lower in the ILC group (0%) than in the IDC group (16.2%) (p = 0.05). In ER+or PR+/HER2-subtype, the mean DFS for the ILC and IDC was 2.9 ± 0.6 and 3.1 ± 0.3 years, and the median survival time after the recurrence for ILC and IDC patients was 4.2 ± 0.7 and 5.6 ± 0.7 years, respectively, with no significant difference (p = 0.77). The frequency of lung metastases was significantly lower in the ILC group (6.3%) than in the IDC group (53.7%) (p < 0.01), while the frequency of peritoneal metastases was significantly higher in the ILC group (68.8%) than in the IDC group (1%) (p = 0.00). Of note, the prognosis after the diagnosis of peritoneal metastases was poor, with a median survival time of 19 ± 9 months and resistance to hormone therapy.
  
  
  CONCLUSIONS
  The extremely high rate (68.8%) of peritoneal metastases was observed in long-term follow-up for the metastatic breast cancer patients with ILC. We need to reveal the definitive feature of ILC and develop new therapeutic strategies to prevent the dissemination of ILCs.
authors.affiliation: Department of Surgery, Yamanashi Prefectural Central Hospital, 1-1-1 Fujimi, Kofu, Japan. inoue-bfgz@ych.pref.yamanashi.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Department of Surgery, Yamanashi Prefectural Central Hospital, 1-1-1 Fujimi, Kofu, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakagomi
authors.affiliation: Department of Surgery, Yamanashi Prefectural Central Hospital, 1-1-1 Fujimi, Kofu, Japan.
authors.forename: Haruka
authors.initials: H
authors.lastname: Nakada
authors.affiliation: Department of Surgery, Yamanashi Prefectural Central Hospital, 1-1-1 Fujimi, Kofu, Japan.
authors.forename: Kazushige
authors.initials: K
authors.lastname: Furuya
authors.affiliation: Department of Surgery, Yamanashi Prefectural Central Hospital, 1-1-1 Fujimi, Kofu, Japan.
authors.forename: Kou
authors.initials: K
authors.lastname: Ikegame
authors.affiliation: Department of Surgery, Yamanashi Prefectural Central Hospital, 1-1-1 Fujimi, Kofu, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Department of Internal Medicine, Yamanashi Prefectural Central Hospital, Kofu, Japan.|University of Tokyo, Tokyo, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Omata
authors.affiliation: Department of Pathology, Yamanashi Prefectural Central Hospital, Kofu, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Oyama
mesh_terms: D000328:Adult; D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy / Q000401:mortality / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000188:drug therapy / Q000401:mortality / Q000473:pathology* / Q000556:secondary; D018275:Carcinoma, Lobular / Q000188:drug therapy / Q000401:mortality / Q000473:pathology* / Q000556:secondary; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000453:epidemiology* / Q000473:pathology / Q000556:secondary; D008207:Lymphatic Metastasis; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy / Q000401:mortality / Q000473:pathology*; D010534:Peritoneal Neoplasms / Q000453:epidemiology* / Q000473:pathology / Q000556:secondary; D011379:Prognosis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D018931:Antineoplastic Agents, Hormonal; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; C508053:ERBB2 protein, human
keywords: Invasive lobular carcinoma (ILC); Metastatic breast cancer; Peritoneal metastases