94 Clinicopathologic Significance of Stromal Inflammation in Invasive Breast Carcinomas

Document Type

Conference Proceeding

Publication Date

3-23-2026

Publication Title

Lab Invest

Keywords

adult, aged, breast cancer, cancer grading, cancer staging, cohort analysis, conference abstract, controlled study, diagnosis, digital pathology, female, histology, human, human cell, human tissue, immunocompetent cell, inflammation, invasive breast cancer, lymph node metastasis, major clinical study, metastasis, pathological complete response, phenotype, retrospective study, stroma, surgery, triple negative breast cancer, tumor microenvironment

Abstract

Disclosures: Omar Abbas: None; Rami Dali: None; Nilesh Gupta: None Background: The tumor microenvironment (TME) plays a critical role in breast cancer biology, yet the clinical relevance of histologic stromal inflammation outside of triple-negative and HER2-positive subtypes remains uncertain. We sought to characterize stromal inflammation across molecular subtypes and treatment settings and assess its association with grade, stage, and pathologic response. Design: A retrospective review of 167 invasive breast carcinomas (treatment-naïve and post-neoadjuvant [NAT]) was performed. Stromal inflammation on biopsy and resection specimens was semi-quantitatively scored as absent, low, moderate, or high. Tumor grade, pathologic T/N stage, and angiolymphatic invasion were recorded. Molecular subtypes: luminal A, luminal B, HER2-enriched, and triple-negative breast cancer (TNBC), were assigned based on marker expression profiles. Statistical associations were analyzed using χ2 and logistic regression models. Results: Stromal inflammation was predominantly low (52.8%), followed by absent (20.2%), moderate (16.6%), and high (10.4%). Inflammation increased with grade and was most frequent in TNBC and HER2-enriched tumors, least in luminal A (p = 0.06). All grade 1 tumors (n = 32) showed absent-to-low inflammation and were mainly luminal A (88%), ≤T1c (94%), and node negative (78%). In grade 2 tumors (n = 51), moderate/high inflammation (19.6%) was associated with higher nodal positivity (OR 2.36, 95% CI 0.43–13.05, p = 0.33). Grade 3 tumors (n = 41) showed moderate/high inflammation in 44% and a stronger trend toward nodal metastasis (OR 4.5, 95% CI 0.9–23.2, p = 0.07). In the post-NAT cohort (n = 36), strict pathologic complete response (pCR) occurred in 28.6% overall, rising from 19.0% in absent/low to 42.9% in moderate/high inflammation (OR 3.19, p = 0.15), predominantly among HER2-positive and TNBC cases. [Formula presented] Conclusions: Stromal inflammation correlates with tumor grade and aggressive molecular subtype, showing a stepwise increase from luminal A to HER2-enriched and TNBC. Although not statistically significant, higher stromal inflammation was consistently associated with greater odds of nodal involvement and higher pathologic response rates after NAT. These findings support stromal inflammation as a reproducible histologic marker of immune activation. Larger studies using digital pathology and AI-based analysis of the TME, including stromal fibrosis, desmoplasia, and immune cell phenotypes, may shed light on these associations and refine immune scoring in breast cancer.

Volume

106

Issue

3

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