Trichorhinophalangeal syndrome 1 expression in breast and nonbreast metastases from Müllerian, lung, gastrointestinal tract, and pancreatic primary tumors by immunohistochemistry with cytology cell block specimens.

Despite high overall sensitivity, TRPS1 showed lower specificity as a breast immunomarker because of its expression in nonbreast tumors. The mean H score in nonbreast tumors was significantly lower than in metastatic breast tumors. It is important to recognize the broad range of expression of TRPS1 in metastatic breast and nonbreast tumors to avoid an incorrect determination of a metastatic tumor's organ of origin.