METHODS: Here, we compared the expression of SOX10 with other breast markers (GATA3, mammaglobin and GCDFP15) and their combined expression in a large cohort of IBC together with nodal metastases. We have also evaluated the expression of GATA3 and SOX10 in a wide spectrum of non-breast carcinomas to assess their value as breast specific markers.
RESULTS: Compared with other markers, SOX10 showed lower overall sensitivity (6.5%), but higher sensitivity in TNBC (31.4%) than other breast markers including GATA3 (29.7% for TNBC). Its expression demonstrated the highest concordance between the paired IBC and nodal metastases (96.4%, κ = 0.663) among all the breast markers. More importantly, SOX10 identified many GATA3-negative TNBC, thus the SOX10/GATA3 combination was the most sensitive marker combination for IBC (86.6%). For non-breast carcinoma, a high SOX10/GATA3 expression rate was found in melanoma (77.9%, predominately expressed SOX10), urothelial carcinoma (82.0%, predominately expressed GATA3) and salivary gland tumors (69.4%). Other carcinomas, including cancers from lungs, showed very low expression for the marker combination.
CONCLUSIONS: The data suggested that SOX10/GATA3 combination can be used for differentiating metastases of breast and multiple non-breast origins. However, the differentiation with melanoma and urothelial tumors required more careful histologic examination, thorough clinical information and additional site-specific IHC markers. For salivary gland tumors, the overlapping tumor types with IBC renders the differentiation difficult.