TRPS1, named for its association with the autosomal dominant genetic disorder TRPS1, has been found to be a critical modulator in mesenchymal-to-epithelial transition during the development and differentiation of several types of tissue, including cartilage, bone, kidney, and hair follicle. Recently, TRPS1 was identified as a novel GATA transcriptional factor, functioning as an essential regulator for the growth and differentiation of normal mammary epithelial cells and possibly involved in the development of breast cancer. A recent study showed that TRPS1, which is highly expressed in triple-negative breast carcinoma (TNBC), was significantly higher than GATA3 expression in metaplastic (85% vs. 21%) and nonmetaplastic (86% vs. 51%) TNBC. Among non-breast tumors, TRPS1 is only expressed in some cases of lung squamous cell carcinoma, urothelial carcinoma (<2%), and ovarian adenocarcinoma. Therefore, TRPS1 has been found to be a highly specific and sensitive marker for all types of breast carcinomas, especially TNBC.