Breast cancer stromal elastosis is associated with mammography screening detection, low Ki67 expression and favourable prognosis in a population-based study

Abstract

Background: Mammography screen-detected breast cancers have a better prognosis than predicted from established prognostic markers. A search for additional features that are characteristic for these tumours and their prognosis is needed to reduce overtreatment, a recognized challenge in breast cancer patient management today. Here, we have investigated the occurrence and importance of tumour elastosis.

Methods: We performed a population based retrospective study of breast cancers detected in the Norwegian Breast Cancer Screening Programme in Vestfold County during 2004-2009. In total, 197 invasive screen-detected cancers and 75 interval cancers in patients aged 50-69 years were compared with regard to standard clinico-pathological parameters and tumour shape, as well as ER, PR, HER2 and Ki67 expression. In particular, the presence of elastotic material in tumours was graded on a 4-tiered scale (score 0-3).

Results: Screen-detected cancers had a significantly higher content of stromal elastosis than interval cancers (p < 0.001). High content of elastosis (score 3) correlated strongly with stellate tumour shape, low histological grade, and ER+/HER2- status. Further, high elastosis score was significantly associated with lower Ki67 expression. In survival analyses, cases with high elastosis demonstrated increased recurrence free (p = 0.03) and disease-specific survival (p = 0.11) compared to cases with low elastosis.

Conclusion: There is a strong correlation between the presence of tumour elastosis, stellate tumour shape and mammography detection of breast cancers. To our knowledge, this is the first time elastosis has been studied in relation to breast cancer detection method. Presence of elastosis is associated with low tumour cell proliferation (Ki67) and a good prognosis.

Virtual slides: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_230.

Figure 1

Histological and radiological images of screen-detected and interval breast cancer. Upper row: Radiological (A) and histological whole tumour images of a screen-detected cancer with stellate shape and abundant stromal elastosis (grade 3) (HES staining in B; elastin-staining in C). Middle row: Comparable images of an interval cancer with rounded, pushing-border contour and no stromal elastosis (grade 0) (D-F). Magnification x 5. Lower row: Higher magnification (x200) of histological slides from the screening cancer in the upper row. G, HES-staining. H, elastin-staining.

Figure 2

High elastosis is significantly associated with low proportion of Ki67 positive tumour cells. The relationship between high/low elastosis and % Ki67 positive tumour cells are demonstrated in the dot-blot.

Figure 3

Elastosis is associated with survival in breast cancer. Low elastosis (evaluated by HES-section) associates with reduced recurrence-free (A) and disease specific (B) survival. For each category, the number of cases is given followed by the number of breast cancer recurrences or deaths.