title: Aggressiveness of breast cancers found with and without screening.
abstract: OBJECTIVE
  To examine how breast cancers found by mammographic screening differ from those found outside screening.
  
  
  METHODS
  Comparative cohort study.
  
  
  METHODS
  Turku, southwestern Finland.
  
  
  METHODS
  126 women aged 40-74 years with breast cancer detected during the first round of mammographic screening in 1987-90 and 125 women within the same age range with breast cancer detected outside screening during the same period.
  
  
  METHODS
  Primary tumour size, axillary nodal status, histological features, oestrogen and progesterone receptor concentrations, ploidy, and S phase fraction.
  
  
  RESULTS
  Compared with the controls women with cancers detected by screening had a smaller primary tumour (57 (46%) screened v 11 (10%) controls had tumours less than or equal to 11 mm in diameter, p less than 0.0001), and less often had axillary nodal metastases (104 (83%) screened v 71 (57%) controls node negative, p less than 0.0001). After adjustment for the smaller size of the primary tumour compared with control cancers, those cancers detected by screening were less likely to have axillary nodal metastases (odds ratio 0.44, 95% confidence interval 0.23 to 0.84), poor histological differentiation (0.20, 0.08 to 0.49), high mitotic counts (0.38, 0.15 to 0.97), tumour necrosis (0.45, 0.22 to 0.93) or to be of the ductal histological type (0.46, 0.22 to 0.95). They had low oestrogen receptor (0.29, 0.12 to 0.70) and progesterone receptor (0.35, 0.17 to 0.92) concentrations less often and had smaller S phase fractions (0.72, 0.55 to 0.96) than control cancers.
  
  
  CONCLUSIONS
  Even after adjustment for the smaller size of screen detected breast cancers, their histological and cytometric features suggest low malignant potential. They may also be less likely to metastasise to axillary lymph nodes than cancers found outside screening.
authors.affiliation: Turku University Hospital, Finland.
authors.forename: P J
authors.initials: PJ
authors.lastname: Klemi
authors.forename: H
authors.initials: H
authors.lastname: Joensuu
authors.forename: S
authors.initials: S
authors.lastname: Toikkanen
authors.forename: J
authors.initials: J
authors.lastname: Tuominen
authors.forename: O
authors.initials: O
authors.lastname: Räsänen
authors.forename: J
authors.initials: J
authors.lastname: Tyrkkö
authors.forename: I
authors.initials: I
authors.lastname: Parvinen
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000737:chemistry / Q000473:pathology*; D016504:Breast Self-Examination; D002452:Cell Count; D015331:Cohort Studies; D005260:Female; D005387:Finland; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology; D008327:Mammography; D008403:Mass Screening; D008875:Middle Aged; D008940:Mitotic Index; D011960:Receptors, Estrogen / Q000032:analysis; D011980:Receptors, Progesterone / Q000032:analysis
chemical_list: D011960:Receptors, Estrogen; D011980:Receptors, Progesterone