Clinical Significance of Grade 1 Triple Negative Breast Cancer: A retrospective cohort analysis

Grade 1 TNBCs comprise of histologically low-grade lesions whose natural histories, molecular features, and optimal therapy vary from those of high-grade TNBCs. Here, we describe the clinopathologic features and outcomes of patients with Grade 1 TNBC. This is a retrospective cohort study on Grade 1 TNBC patients from two separate Regional Cancer Programs in Canada seen from January 1, 2004 to December 31, 2022 . Demographic data, tumor characteristics, treatment and outcome of patients with TNBC from the two institutions were collected and analyzed. We identified a different pattern of histology for Grade 1 TNBC where 17 of 19 (89.4%) patients had infiltrating ductal disease, in contrast to literature which reported either carcinoma with salivary gland like morphology or low grade lesions considered benign as the more common histology pattern. Five had breast cancer recurrence indicating a recurrence rate of 26.3%. Out of the 5 patients with recurrence, one was stage 3, three were stage 2 and one was stage 3. All three patients (15.7%) who died from cancer were stage 2. TNBC patients with grade 1 tumors in this study were shown to have a different histology from that reported in literature and more similar to other grades of TNBC. The study also showed recurrence rate in more than a quarter of the cases . The relapse pattern is not dissimilar to other grades of TNBC and according to this study does not represent a unique subset of TNBC.