Many genetic abnormalities disclosed even in somatic cells like peripheral blood lymphocytes may mark footprint(s) of malignancy(ies). The present cytogenetic study on peripheral blood lymphocytes of sporadic breast cancer patients (n = 20) and their first degree relatives (n = 39) reports abnormalities of chromosomes 16, 5, 12, and 17 respectively in 17.59%, 8.33%, 6.48%, and 5.57% cells of patients and 15.83%, 8.33%, 7.5%, and 5% cells of their first degree relatives. These common chromosomal abnormalities pave the way to assume why first degree relatives of sporadic breast cancer patients are at increased risk of developing the same or other malignancies.