title: The importance of MUC1 cellular localization in patients with breast carcinoma: an immunohistologic study of 71 patients and review of the literature.
abstract: BACKGROUND
  The MUC1 mucin is present on the apical surface of normal secretory epithelia. In breast carcinoma, MUC1 expression is variable in amount and cellular localization, the significance of which is controversial. The authors undertook a detailed analysis of staining pattern combined with a comprehensive literature review to better understand the role of MUC1 in breast carcinoma.
  
  
  METHODS
  Seventy-one patients with breast carcinoma were examined for MUC1, beta-catenin, and E-cadherin staining patterns. These data were compared with data from 25 articles from the literature examining the expression of MUC1 in breast carcinoma.
  
  
  RESULTS
  All invasive carcinomas showed some MUC1 staining. In invasive ductal carcinomas, MUC1 was detected in the apical membrane (15%), cytoplasm (93%), or circumferential membrane (13%), with 81% of tumors showing a mixture of patterns. Tumors with low overall MUC1 expression (< or = 50% positive tumor cells) had a higher nuclear grade than tumors with high overall MUC1 expression (> 50%; P = 0.01). Tumors with high and low cytoplasmic expression had no difference in nuclear grade (P > 0.3). Circumferential membrane staining was correlated with positive lymph node status (P = 0.011).
  
  
  CONCLUSIONS
  In the literature, similar findings prevailed in which overall MUC1 expression was increased in lower grade (10 of 14 studies), estrogen receptor positive (8 of 13 studies) tumors and was associated with a better prognosis (8 of 13 studies). High cytoplasmic staining was associated with a worse prognosis, an association that was not explained by differences in histologic grade. Thus, the presence of MUC1 in the majority of tumor cells is associated with better differentiated tumors and with an improved prognosis. However, aberrantly localized MUC1 in the tumor cell cytoplasm or nonapical membrane is associated with a worse prognosis.
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Alberta, Cross Cancer Institute, Edmonton, Alberta, Canada.
authors.forename: J J
authors.initials: JJ
authors.lastname: Rahn
authors.forename: L
authors.initials: L
authors.lastname: Dabbagh
authors.forename: M
authors.initials: M
authors.lastname: Pasdar
authors.forename: J C
authors.initials: JC
authors.lastname: Hugh
mesh_terms: D001943:Breast Neoplasms / Q000503:physiopathology*; D002277:Carcinoma / Q000503:physiopathology*; D018270:Carcinoma, Ductal, Breast / Q000503:physiopathology*; D002454:Cell Differentiation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D018396:Mucin-1 / Q000032:analysis* / Q000494:pharmacology; D009361:Neoplasm Invasiveness; D011379:Prognosis
chemical_list: D018396:Mucin-1