The World Health Organization (WHO) reports that approximately 2.3 million breast cancer cases are diagnosed each year. Early detection is key to tackling this issue, and Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCE‐MRI) is a preferred method for detecting tumors. Convolutional Neural Networks (CNNs) can accurately segment images without human assistance. The objective of this study is to develop a computer‐aided diagnosis system that can segment breast lesions from DCE‐MRI images. A 92‐layer deep CNN, called DCNN‐92, and a 94‐layer deep CNN, called DCNN‐94, have been designed to identify lesions. The proposed methods have been validated using images from The Cancer Image Archive (TCIA) database. The proposed DCNN‐92 model segments the tumor pixels effectively, but it exhibits some misclassifications where certain background pixels are incorrectly labeled as tumor and tumor pixels are identified as background. To segment the tumor pixels more accurately, two grouped convolution layers are added to the DCNN‐92 model. The model with 94 layers, that is, DCNN‐94, segments most of the tumor pixels correctly, thereby enhancing the segmentation performance. When compared to DCNN‐92, the DCNN‐94 model exhibits enhanced performance across standard metrics such as sensitivity, dice coefficient, Jaccard coefficient, and area under the curve (AUC). It was found that the training time for DCNN‐94 is shorter. The DCNN‐94 model with dilation factor and group convolution is concluded to be an effective method for lesion segmentation from breast DCE‐MRI images compared to existing methods.