Malignant Mixed Tumor of the Skin With TRPS1::PLAG1 Fusion

ABSTRACT: Malignant mixed tumor of the skin (MMTS) is an extremely rare malignant cutaneous adnexal neoplasm that arises through malignant transformation of a benign mixed tumor of the skin and exhibits a variety of histopathological features. Benign mixed tumor of the skin is classified morphologically into apocrine and eccrine types; the former being characterized molecularly by PLAG1 rearrangement. To date, approximately 50 cases of MMTS have been reported, but most published case reports have not been supported by molecular pathological analysis. In this study we report the first documented case of MMTS in which a TRPS1::PLAG1 fusion gene was identified. Further accumulation of MMTS cases with detailed molecular analysis, focusing particularly on PLAG1 rearrangement and overexpression, is warranted.