en Cancer Cancer Original Article Original Article StAR related lipid transfer domain containing 3 (<em>STARD3</em>) gene has been reported to be co-amplified with human epidermal growth factor receptor 2 (<em>HER2</em>) in breast carcinoma. STARD3 is necessary for cholesterol transfer and metabolism in tumor cells. The possible role played by <em>STARD3</em> as a diagnostic and prognostic biomarker was investigated in breast cancer (BC). Data mining was performed using several bioinformatics websites to investigate the correlation of <em>STARD3</em> with BC and its molecular subtypes, and conventional PCR was used to detect the <em>STARD3</em> mRNA levels in a panel of BC cell lines. <em>STARD3</em> was overexpressed in BC more <span dir="RTL">than the</span> other types of cancer. The results also showed that <em>STARD3</em> expression was significantly associated with HER2⁺ BC tumors and BC cell lines, and low STARD3 mRNA and protein expression levels were observed in estrogen receptor-positive (ER⁺) and triple-negative BC (TNBC) patients. Moreover, high <em>STARD3</em> expression levels predicted worse overall survival (OS), relapse-free survival (RFS) and disease metastasis-free survival (DMFS) in BC, and HER2⁺ BC. Notably, low expression of <em>STARD3</em> was associated with poor OS in ER⁺ BC. Our findings suggest that <em>STARD3</em> may have strong diagnostic and prognostic value for HER2⁺ breast carcinoma. Breast neoplasm, STARD3, HER2, prognosis, computational biology 34 44 http://ijmcmed.org/browse.php?a_code=A-10-3339-1&slc_lang=en&sid=1 Abdul Fattah Salah Fararjeh Fararjehas@bau.edu.jo 100319475328460020496 0002-2850-7001 Yes Department of Medical Laboratory Analysis, Faculty of Science, Al-Balqa Applied University, Al-salt, Jordan. Ali Al Khader ali.alkhader@bau.edu.jo 100319475328460020497 0001-8453-3629 No Department of Pathology and Forensic Medicine, Al-Balqa Applied University. Ezidin Kaddumi kaddumi@bau.edu.jo 100319475328460020498 100319475328460020498 No Department of Basic Medical Sciences, Faculty of Medicine, Al-Balqa Applied University, Al-salt, Jordan. Maher Obeidat obeidat@bau.edu.jo 100319475328460020499 100319475328460020499 No Department of Medical Laboratory Analysis, Faculty of Science, Al-Balqa Applied University, Al-salt, Jordan. O'la AL-Fawares ola.alfawares@bau.edu.jo 100319475328460020500 100319475328460020500 No Department of Medical Laboratory Analysis, Faculty of Science, Al-Balqa Applied University, Al-salt, Jordan.