LAUSR

Metastatic breast carcinoma (mBC) is frequently encountered and may be challenging to diagnose as the tumor cells can morphologically resemble carcinomas of other primary origins. An additional challenge is that direct smears are often the only sample type available for immunostaining studies in cytology. Trichorhinophalangeal syndrome GATA‐binding type 1 1 (TRPS1) is a highly sensitive marker for BC compared to the commonly used marker GATA3, especially in triple‐negative BC (TNBC), in histologic samples. However, its sensitivity and specificity in mBC and other GATA3‐positive tumors have not been studied.