Two patients without evidence of MSI by PCR and targeted NGS had pathogenic or likely pathogenic germline and somatic MMR gene alterations One patient with MSI (case 5) had no pathogenic or likely pathogenic MMR genes and other DDR pathway gene alterations, however, the patient had likely pathogenic mutations in ARID1A, JAK1, and APC. The ductal adenocarcinoma (DAC) of case 6 also had a likely pathogenic mutation in ARID1A and pathogenic mutations in BRAF and JAK3. Here, JAK1 is linked to invasive ductal breast carcinoma.