Collagen Fiber Alignment in Relation to Prognostic Markers for Ductal Carcinoma In Situ of the Breast

Abstract

Almost 20% of new diagnoses of breast cancer are ductal carcinoma in situ (DCIS). DCIS increases risk for invasive breast cancer, and new prognostic markers of disease-free survival are needed to complement the few that are known. Limited studies have investigated the prognostic value of the tumor microenvironment, which is increasingly recognized as potentially playing a key role in tumor invasion and progression. Collagen is the most abundant component of the stroma surrounding the breast ducts, and laboratory studies suggest that collagen alignment facilitates cancer cell invasion and migration. Here we examined whether collagen alignment patterns in human DCIS specimens correlate with known prognostic markers. We evaluated collagen fiber alignment in 235 Wisconsin women diagnosed with DCIS in 1997–2000 who participated in a clinicopathologic cohort study. Fiber alignment was evaluated from routine H&E tissue slides prepared at the time of diagnosis using second harmonic generation (SHG) microscopy, a label-free multiphoton laser scanning technique that selectively images collagen. Images were evaluated for the presence of collagen fibers arranged in a radial pattern (approximately 75- to 90-degree angles) with respect to the DCIS lesion/stroma boundary, a phenotype termed TACS (Tumor Associated Collagen Signature). Chi-square tests were used to compare presence or absence of TACS with prognostic factors from a central review of pathology reports and slides, and analysis of tissue for ER, PR, Ki-67, and HER2. Overall, slides for about half (49.8%) of DCIS cases showed the TACS phenotype. TACS was not associated with age of the cases (P = 0.29), size of the lesion (P = 0.76), grade (P = 0.61), or margin size (P = 0.77). However, results suggested that TACS was more common (63.1%) among DCIS cases detected symptomatically than by mammography (47.3%, P = 0.09). TACS was more common among cases that were ER-negative (P = 0.002), PR-negative (P = 0.02), Ki-67 positive (P = 0.06), and HER2-positive (P = 0.002). This study underscores the relevance of the tumor microenvironment, in particular the arrangement of the collagen fiber matrix. On-going analysis will examine disease-free survival among DCIS cases according to patterns of collagen fiber alignment.