Abstract

Objectives: Tenascin-C (TNC) is an extracellular matrix protein associated with tissue remodeling, tumor progression, and poor prognosis in breast cancer. Although TNC has attracted interest as a potential stromal biomarker, its baseline histopathological distribution in untreated breast cancer has not been fully characterized. This exploratory pilot study aimed to characterize the immunohistochemical distribution of TNC in representative treatment-naïve breast cancer tissues. Methods: Immunohistochemical staining for TNC was performed in representative breast cancer tissue specimens obtained from 16 treatment-naïve patients encompassing major histological and molecular subtypes. Tumor and non-tumor areas were evaluated descriptively by two board-certified pathologists using consensus assessment. Results: Heterogeneous TNC expression was observed in the stroma surrounding invasive tumors in all cases. In most specimens, TNC staining was predominantly localized to the peritumoral stroma, whereas occasional staining was observed around non-invasive lesions. Non-tumor breast stroma was largely negative, although positive staining was observed in biopsy scars and sclerotic areas. No consistent subtype-specific pattern of TNC distribution or staining intensity was identified. Conclusions: TNC showed heterogeneous stromal expression in treatment-naïve breast cancer and was also detected in biopsy scars and areas of stromal remodeling. These findings provide baseline histopathological information regarding TNC localization in untreated breast cancer. Further studies are required to determine the potential clinical utility of TNC as a stromal biomarker, including its application in the post-neoadjuvant setting.

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