Abstract

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.