Breast cancer cell lines and mouse models are valuable tools for investigating the biology of and developing potential therapeutics for human breast carcinoma. The PTEN-/-/NIC mouse is a genetically engineered mouse model for ErbB2/Neu-overexpressing/‑PTEN deficient breast carcinoma with histopathological and molecular features relevant to the luminal subtype of primary human breast cancer. However, the PTEN-/-/NIC model develops multifocal and aggressive mammary tumors with a short life-span, which greatly impedes its preclinical usage. To complement the genetic engineering approach and to facilitate the future application of this model, in the present study, two newly established cell lines, NICP20 and NICP21, from PTEN-/-/NIC mammary tumors are described. These NICP20 and NICP21 cells retained the crucial molecular phenotype similar to the origin, as confirmed by genotyping and western blot analysis. These cells induced tumors in immunocompetent syngeneic mice by mammary fat pad injection and produced lung metastasis when injected intravenously. Tumors induced by these cells displayed luminal‑like histologic morphology and hyperactivation of Akt which are similar to PTEN-/-/NIC tumors. Immunohistochemical staining also revealed that tumors induced by the NICP20 and NICP21 cells showed a high proliferative level, comparable angiogenesis and T-cell infiltration properties similar to PTEN-/-/NIC tumors. Therefore, these NICP20 and NICP21 cells represent an alternative and useful model system to enhance our understanding of the nature of ErbB2-positive breast cancers, particularly accompanying PTEN loss and to facilitate further experimental therapeutic studies.