What happened, in summary

This 37-year-old woman was the proband in a familial breast cancer genetics evaluation. She was diagnosed with triple-negative invasive ductal carcinoma in the outer upper quadrant of the breast. Pathology described WHO grade 3 disease with a microscopic invasive focus measuring about 0.5 cm and pathologic stage ypT1aN0(sn)Mx. Immunohistochemistry showed ER-negative, PR-negative, HER2 1+ / HER2-negative disease, Ki-67 20%+, CK5/6-negative staining, scattered P63 positivity, E-cadherin positivity, AR negativity, and GCDFP-15 negativity. Breast ultrasound showed a solid hypoechoic nodule in the right breast at the 10 o’clock position, measuring 2.2 × 1.6 × 1.7 cm, BI-RADS 4b, with a right axillary lymph node visualized. She underwent modified radical mastectomy combined with sentinel lymph node dissection, then received postoperative nursing care and follow-up. Her evaluation also included hereditary risk across her family. Investigators studied 32 relatives, collected blood samples from selected affected and unaffected members, performed whole-exome sequencing, and validated findings with Sanger sequencing. The affected family members with breast cancer carried concurrent heterozygous deletions in BRCA1 and OBSCN. In contrast, sampled relatives with isolated BRCA1, HMMR, or OBSCN alterations did not show abnormal clinical features. The authors suggested that BRCA1 was the main driver of hereditary risk, while OBSCN may modify disease expression in an oligogenic model. For this patient, the important clinical summary is small node-negative triple-negative breast cancer treated surgically, with familial BRCA1/OBSCN co-deletion identified for counseling and surveillance of relatives. The same family analysis also found that HMMR variants alone did not explain the breast cancer pattern, so the BRCA1/OBSCN combination carried the main clinical relevance.