Characterization of Fibrotic Focus as a Prognostic Marker in Breast Cancer

Background Breast cancers exhibit a wide scope of morphologic features with demonstrated prognostic significance. These features have the advantage of easily evaluated in routine reporting; thus offering great clinical potential. In our earlier analysis, fibrotic focus (FF) was demonstrated to have added value to the current staging. FF refers to the central scar like area in an invasive tumor, and is surrounded by a highly cellular zone of infiltrating tumor cells. It is composed of fibroblasts and collagen fibers forming a radially expanding fibrosclerotic core, with an incidence of around 20%. The precise composition of the different components within FF may affect its prognostic value in breast cancer.

Cancer-associated fibroblasts (CAF) and collagen components are the most prominent features in FF. FF with proliferative CAF was associated with higher risk of metastasis. Moreover, CAFs identified by fibroblastic markers were correlated with breast cancer recurrence. In breast cancer, different subsets of CAF by differential fibroblastic markers have been characterized recently. They were present in varying proportions in breast cancer subtypes and conferred dissimilar impact on the immune tumor microenvironment (TME). Nonetheless, the relationship of CAF subtypes and FF and whether they will affect the FF prognostic impact remain elusive. Apart from CAF, the potent influence of collagen content in cancer is increasingly appreciated. Collagen stroma can modulate immune TME by inhibiting CD8 T lymphocytes infiltration. The expression of collagen and other extracellular matrix components is prognostic in different types of cancer patients, including breast cancer. For FF, detailed analysis on the collagen content is still lacking. The distinct collagen composition and organization could also impact on the prognostic capabilities of FF. The underlying mechanisms for effects of FF are largely unknown. To date, there are very few reports of molecular analysis of breast cancers with FF. FF has been associated with increased angiogenesis, hypoxia markers expression and activation of hypoxia-inducible factor-1α pathway, and concordantly increased tumor associated macrophage (TAM) infiltration. Exploration of other key biomarkers involved in will provide additional information on FF prognostication.

In this proposal, a systemic evaluation on the FF features in breast cancers will be performed. We aim to further characterize FF at different levels in detail. Finally, we plan to develop prognostic model integrating the different FF features for a more accurate risk stratification.

Study design To characterize FF based on morphologic, structural and molecular features The different morphologic features of FF will be examined and correlated with the clinico-pathologic parameters and breast cancer subtypes. To characterize the collagen stroma, the expression of these different collagens will be determined by IHC analysis. The structural characteristics of the collagen fibers will be determined on SHG signal and/or pico-Sirius red staining. The collagen composition and structural features in cases with different FF morphological features will be compared.

For the characterization of fibroblastic components, CAF populations will be determined by IHC analysis. Based on the reported CAF phenotypes, CAF markers will be examined on the consecutive IHC slides. Co-expression of CAF markers will be evaluated using multiple IHC alignment. The relationship of CAF subpopulations on FF and collagen features as well as clinico-pathologic characteristics will be examined.