Prognostic significance of nucleolar assessment in invasive breast cancer

Aims: Nucleolar morphometric features have a
potential role in the assessment of the aggressiveness
of many cancers. However, the role of nucleoli in
invasive breast cancer (BC) is still unclear. The aims
of this study were to investigate the optimal method
for scoring nucleoli in IBC and their prognostic significance,
and to refine the grading of breast cancer
(BC) by incorporating nucleolar score.
Methods and results: Digital images acquired from
haematoxylin and eosin-stained sections from a large
BC cohort were divided into training (n = 400) and
validation (n = 1200) sets for use in this study. Four
different assessment methods were evaluated in the
training set to identify the optimal method associated
with the best performance and significant prognostic
value. These were: (i) a modified Helpap method; (ii)
counting prominent nucleoli (size ≥2.5 μm) in 10
field views (FVs); (iii) counting prominent nucleoli in
five FVs; and (iv) counting prominent nucleoli in one
FV. The optimal method was applied to the validation
set and to an external validation set, i.e. data from
The Cancer Genome Atlas (n = 743). Scoring prominent
nucleoli in five FVs showed the highest interobserver
concordance rate (intraclass correlation
coefficient of 0.8) and a significant association with
BC-specific survival (P < 0.0001). A high nucleolar
score was associated with younger age, larger
tumour size, and higher grade. Incorporation of
nucleolar score in the Nottingham grading system
resulted in a higher significant association with survival
than the conventional grade.
Conclusions: Quantification of nucleolar prominence
in five FVs is a cost-efficient and reproducible morphological
feature that can predict BC behaviour and
can provide an alternative to pleomorphism to
improve BC grading performance.