Background Trophoblast cell-surface antigen 2 (TROP2) is related to tumor proliferation enhancement and poor prognosis. An antibody targeting TROP2 was developed to treat metastatic triple-negative breast cancer (TNBC) which has a limited treatment modality. To characterize the TROP2 expressing tumors in TNBC, we analyzed TROP2 expression in three cohorts; (1) primary tumor without neoadjuvant chemotherapy, (2) primary tumor with neoadjuvant chemotherapy, and (3) metastatic tumor. Methods A total of 807 TNBC cases were evaluated for TROP2 immunohistochemical expression. We evaluated the TROP2 H-score distribution in the three cohorts. Tumors were divided into two groups based on TROP2 expression (high vs. low). We analyzed the relationship between clinicopathologic features and markers, including epidermal growth factor receptor, cytokeratin 5/6, p53, and Ki-67, and prognostic significance at high vs. low TROP2 expression. Results There was no difference in TROP2 H-score distribution between the three cohorts. Moderate-to-strong membranous expression of TROP2 in at least 10% of tumor cells was present in 662 cases (82.0%) in Cohort 1, 59 cases (89.4%) in Cohort 2, and 23 cases (88.5%) in Cohort 3. There was no significant difference in clinicopathologic features between high vs. low TROP2 in all cohorts. TROP2 H-score was an independent poor prognostic factor for overall survival in Cohort 3. Conclusions TNBC showed similar TROP2 expression regardless of neoadjuvant treatment or primary tumor/metastasis. Although the prognostic significance of TROP2 expression in metastatic TNBC has been revealed, further evaluation of the predictive value of TROP2 expression for targeted therapy is needed.

<b><i>Background/Aims:</i></b> The presence and clinical importance of tissue-resident memory T (T_RM) cells have been recently described in association with various cancer types. However, the frequency and the traditional naïve–effector–memory phenotypic characteristics of T_RM cells are largely unknown. <b><i>Methods:</i></b> We analyzed single-cell populations of colorectal cancer (CC, <i>n</i> = 18), stomach cancer (SC, <i>n</i> = 13), renal cell carcinoma (RCC, <i>n</i> = 19), and breast cancer (BC, <i>n</i> = 16) by dissociation of tumor tissue with collagenase/hyaluronidase. We investigated populations of naïve, effector, and memory T and T_RM cells by flow cytometry. <b><i>Results:</i></b> Among CD8⁻ cells, CC was associated with a significantly higher proportion of CD103⁺ T cells than other tumor types (<i>p</i> &#x3c; 0.001). Among CD8⁺ cells, CC and SC were associated with higher CD103⁺ T-cell proportions than RCC and BC (<i>p</i> &#x3c; 0.001). Significantly more CD8⁺ than CD8⁻ cells expressed CD103 (<i>p</i> &#x3c; 0.001). In association with SC, RCC, and BC, CD8⁺ T cells had a similar T-cell phenotype composition pattern: fewer effector T cells and more memory-type T cells among CD103⁺ cells compared with CD103⁻ cells (<i>p</i> &#x3c; 0.05). Tumors with higher proportion of CD103⁺ cells had no specific clinicopathologic characteristics than those with lower proportion of CD103⁺ cells. <b><i>Conclusion:</i></b> T_RM cell abundance and phenotypes varied among CC, SC, RCC, and BC. Further studies regarding the functional differences of T_RM associated with various tumors are warranted.