VIM and undifferentiated (embryonal) sarcoma: Additionally, vimentin has been reported to be positive in a number of ATC.58, 59 A strong, predominantly cytoplasmic positivity for CD1d seems very characteristic for ATC, while other poorly differentiated neoplasms that can occur in the mediastinum, for example undifferentiated sarcomas or metastases of malignant melanoma, show either negative staining for CD1d or a predominantly membranous pattern.