Relationship between laterality and clinicopathological characteristics in patients with breast cancer: A retrospective cross-sectional study

Objectives: To compare the incidence of right- and left-sided breast cancer (BC) according to the age at diagnosis, sex, involved quadrants, grade, estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2) status. Design: A retrospective cross-sectional study Setting: A tertiary university hospital in Riyadh, Saudi Arabia Subjects: We included 142 patients diagnosed with invasive breast carcinoma between January 2017 and December 2018. Interventions: No intervention was performed. Main outcome measures: Demographic data were collected from the hospital's medical records. Information on the diagnoses and ER/PR/HER-2statuswas obtained by reviewing the patients' histopathological and immunohistochemistry reports, and the fluorescence in situ hybridization (FISH) report for the HER-2 patients, respectively. Results: Unilateral and bilateral BCs were detected in 93% and 7% of the patients, respectively. Overall, 74 (52%) patients had left-sided and 58 (41%) had right-sided BC. The age range in both groups was 45-54 years. Both right-sided (53%) and left-sided (46%) BCs were most common in the upper outer quadrant. Surprisingly, all HER-2 equivocal cases on immunohistochemistry that were amplified on FISH were left-sided BCs. There was no significant relationship between laterality and tumor grade. Compared to right-sided and bilateral tumors, left-sided tumors were more likely to be ER-negative, PR-negative and HER-2-negative. Conclusions: Newly diagnosed BC patients could have both left and right-sided BC. Interestingly, all equivocal HER-2 cases on immunohistochemistry that were amplified on FISH were left-sided BCs. Hence, the primary tumor location may be considered when systematically evaluating and screening BC patients.