Background and purpose: The 4T1 cell line is a laboratory model used in the study of tumors biology. This cell line is very tumorigenic with high metastatic capacity in different organs. In this study, histology and immunohistochemistry methods were used to investigate the structure and localization of Na⁺/K⁺- ATPase enzyme in 4T1 cells induced breast cancer tumor in Balb/c nu mice.

Materials and methods: The histological sections (4 µm) were stained using Hematoxilin-Eosin and IgGα₅ special antibody was used for immunohistochemistry study.

Results: Study of tumor structure showed abnormal proliferation and high mitogenicity in epithelial cells with high proliferation rate. Immunohistochemistry analysis revealed significant immunofluorescence, indicating abundant presence of Na⁺/K⁺-ATPase enzymes (sodium potassium pump) in tumor cells.

Conclusion: Current results showed high rate of sodium potassium pump in plasma membrane of tumor cells. Immunofluorescence characteristic of 4T1 tumor cell lines make them appropriate candidate for antitumor studies.