title: A study of interval breast cancer within the NHS breast screening programme.
abstract: OBJECTIVE
  To define the biological nature and malignant potential of interval cancers presenting to a breast unit within the NHS breast screening programme.
  
  
  METHODS
  112 interval cancers were compared with matched, screen detected and symptomatic cancers in terms of their radiographic, histopathological, and immunohistochemical features.
  
  
  RESULTS
  Interval cancers, strictly defined, showed no characteristic radiographic pattern. In terms of size, vascular invasion, lymph node status, and prognosis they were intermediate between screen detected and symptomatic cancers. Within the interval cancers there was an excess of grade 1 and grade 3 tumours, and lesions with a high Ki67 index but immunohistochemistry otherwise failed to discriminate between the three groups. Inclusion of data from false negative "interval cancers" did not significantly alter the results.
  
  
  CONCLUSIONS
  Interval cancers are more aggressive than screen detected cancers but in general less aggressive than symptomatic cancers. However, within a heterogeneous group, occasional interval cancers are exceptionally malignant.
authors.affiliation: Breast Unit, Queen Elizabeth Hospital, Gateshead, UK.
authors.forename: W K
authors.initials: WK
authors.lastname: Cowan
authors.forename: B
authors.initials: B
authors.lastname: Angus
authors.forename: J C
authors.initials: JC
authors.lastname: Gray
authors.forename: L G
authors.initials: LG
authors.lastname: Lunt
authors.forename: S R
authors.initials: SR
authors.lastname: al-Tamimi
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D019394:Ki-67 Antigen / Q000378:metabolism; D008207:Lymphatic Metastasis; D008403:Mass Screening; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D011379:Prognosis; D011859:Radiography; D016037:Single-Blind Method; D013222:State Medicine; D013997:Time Factors; D006113:United Kingdom
chemical_list: D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen