The Added Value of SOX10 Immunohistochemistry to Other Breast Markers in Identifying Cytokeratin 5-Positive Triple Negative Breast Cancers as of Mammary Origin.

AIMS

Triple-negative breast cancer (TNBC) represents a specific group that lacks the expression of estrogen receptors, progesterone receptors, and human epidermal growth factor receptor-2 and might also lack the expression other breast markers like GATA3, mammaglobin (MG), GCDFP15 (growth cystic disease fluid protein 15), and NYBR1; when this occurs, proving the breast origin of a metastasis is a challenging task. In the present study, we assessed the added value of SOX10 immunohistochemistry to known GATA3, MG, GCDFP15, and NY-BR-1 statuses in a series of CK5-positive primary TNBCs.

METHODS

Tissue microarrays were made from the formalin-fixed and paraffin-embedded blocks of 120 TNBCs, and 3-4-mm-thick sections were immunostained for SOX10. The cut-off for a positive reaction was at least 10% of tumor cells staining.

RESULTS

In our cohort, SOX10 positivity was seen in 82/119 cases, 61, 74, 76, and 82 all of which were GATA3, MG, GCDFP15, and NY-BR-1 negative, respectively. Of the SOX10 negative cases, 12 stained with at least another breast marker. Nevertheless, 25/119 (21%) cases remained negative with all markers assessed.

DISCUSSION

SOX10 proved to be the most commonly positive breast marker in our CK5 expressing TNBCs, but the other markers also had some additive value to SOX10.