A diagnostic dilemma can be encountered when primary triple-negative breast carcinoma (TNBC) without an in situ component or metastatic TNBCs lose the currently used organ-specific marker such as GATA3, raising concerns about metastatic carcinoma from other sites. In the current study, we compared the newly identified breast marker TRPS1 with currently used breast markers GATA3 and SOX10 in whole-tissue sections from 315 cases of various subtypes of TNBC. TRPS1 was highly expressed in 100% of triple-negative primary and metastatic invasive lobular carcinomas, 99% of triple-negative primary and metastatic invasive breast carcinoma of no special type (IBC-NST), and 95% of metaplastic breast carcinomas. In contrast, GATA3 and SOX10 were expressed in 94% and 0% of invasive lobular carcinomas, 63% and 74% of IBC-NST, and 50% and 49% of metaplastic breast carcinomas, respectively. For special-type TNBCs, both TRPS1 and GATA3 were negative in acinic cell carcinomas, most cribriform adenoid cystic carcinomas, and neuroendocrine carcinomas, but positive in secretory carcinomas. Triple-negative apocrine carcinoma was the only subtype of TNBC with positive GATA3 but negative TRPS1. These data indicate that TRPS1 is a highly sensitive marker for TNBCs with positivity not only in GATA3/SOX10-positive TNBCs but also in almost all GATA3/SOX10-negative TNBCs.
Keywords: GATA3; Invasive breast carcinoma of no special type; Invasive lobular carcinoma; Metaplastic carcinoma; SOX10; TRPS1; Triple-negative breast carcinoma.
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