NHSBSP type 1 interval cancers: a scientifically valid grouping?

Clin Radiol. 2007 Mar;62(3):262-7. doi: 10.1016/j.crad.2006.10.002.


Aim: To assess whether there are differences in the pathological features or survival between the new National Health Service Breast Screening Programme (NHSBSP) interval cancer classification system category of type 1 interval cancers, and the previously used, separate categories of occult, unclassified, and true interval cancers.

Materials and methods: The prognostic pathological features (grade, lymph node stage, size, vascular invasion, oestrogen receptor status, and histological type) and survival of 428 type 1 interval invasive breast cancers were analysed by subgroup (occult, unclassified and true interval).

Results: Occult cancers compared with other type 1 interval cancers were of significantly lower grade [38 of 52 (73%) versus 151 of 340 (44%) grade 1 or 2, p=0.0005], more likely to be smaller size [37 of 51 (73%) versus 158 of 341 (46%) <20mm, p=0.0003] and more frequently of lobular type at histology [14 of 42 (32%) versus 50 of 286 (17%), p=0.03]. There was no significant difference in pathological features of unclassified tumours compared with other type 1 tumours. There was no significant survival difference between different type 1 subgroups (p=0.12).

Conclusion: The NHSBSP type 1 interval cancers are a heterogeneous grouping with markedly differing pathological features. However, no significant survival difference is seen between the different type 1 subgroups.

MeSH terms

  • Biomarkers, Tumor / analysis
  • Breast Neoplasms / classification
  • Breast Neoplasms / diagnostic imaging
  • Breast Neoplasms / pathology*
  • Female
  • Humans
  • Lymphatic Metastasis
  • Mammography
  • Mass Screening* / standards
  • Middle Aged
  • Neoplasm Invasiveness
  • Neoplasm Staging
  • Prognosis
  • Receptors, Estrogen / analysis
  • State Medicine
  • Survival Analysis
  • United Kingdom


  • Biomarkers, Tumor
  • Receptors, Estrogen