BREAST Usefulness of imaging findings in predicting tumor-infiltrating lymphocytes in patients with breast cancer Filiz Çelebi 1 & Filiz Agacayak 2 & Alper Ozturk 3 & Serkan Ilgun 4 & Muhammed Ucuncu 5 & Zeynep Erdogan Iyigun 6 & Çetin Ordu 7 & Kezban Nur Pilanci 8 & Gul Alco 9 & Serap Gultekin 10 & Emetullah Cindil 10 & Gursel Soybir 11 & Fatma Aktepe 12 & Vahit Özmen 13 Received: 26 July 2019 /Revised: 26 September 2019 /Accepted: 16 October 2019 # European Society of Radiology 2019 Abstract Objectives Tumor-infiltrating lymphocytes (TILs) have been determined as a new prognostic indicator of immunotherapy response in breast cancer (BC). The aim of this study is to investigate the effectiveness of imaging features in predicting the TIL levels in invasive BC patients. Methods A total of 158 patients with invasive BC were included in our study. All lesions were evaluated based on the BIRADS lexicon. US was performed for all the patients and 89 of them underwent MRI. The histologic stromal TIL (sTIL) levels were assessed and associations between the sTIL levels and imaging features were evaluated. Results Tumors with high sTIL levels had more circumscribed margins, round shape, heterogeneous echogenicity, and larger size on ultrasonography (p < 0.005). There was a statistically significant positive correlation between the sTIL levels and ADC value (p < 0.001). Tumors with high sTIL levels had significantly more homogeneous enhancement than the tumors with low sTIL levels (p = 0.001). Logistic regression analysis showed that the ADC was the most statistically significant parameter in predicting the sTIL levels (the odds ratio was 90.952; p = 0.002). The optimal cutoff value for ADC in predicting low and high sTIL levels was found to be 0.87 × 10 -3 mm 2 s -1 (AUC = 0.726, 73% specificity, and 60% sensitivity). Conclusions Imaging findings, especially the ADC, may play an important role as an adjunct tool in cases of uncertain situations and may improve the accuracy of biopsy results. The prediction of sTIL levels using imaging findings may give an opportunity to predict prognosis. Key Points • Preoperative assessment of TILs is an important biomarker of prognosis and treatment efficacy. • ADC value can be a useful tool in distinguishing high and low sTIL levels as a non-invasive method. • The prediction of sTIL levels using imaging findings may give an opportunity to predict prognosis and an optimal treatment for the BC patients. Keywords Tumor . Lymphocytes . Breast cancer . Diffusion . Magnetic resonance imaging Abbreviations ADC Apparent diffusion coefficient AUC Area under the curve BC Breast cancer BI-RADS Breast Imaging Reporting and Data System DWI Diffusion-weighted imaging ER Estrogen receptor HER2 Human epidermal growth factor receptor 2 IHC Immunohistochemical Lum Luminal MRI Magnetic resonance imaging NAC Neoadjuvant chemotherapy pCR Pathological complete response ROC Receiver operating characteristic analysis TIL Tumor-infiltrating lymphocyte TN Triple negative US Ultrasonography * Filiz Çelebi elbuken.filiz@gmail.com Extended author information available on the last page of the article https://doi.org/10.1007/s00330-019-06516-x European Radiology (2020) 30:2049–2057 /Published online: 10 December 2019