Molecular genetic findings in two cases of sarcomatoid carcinoma of the ureter: evidence for evolution from a common pluripotent progenitor cell?

The current World Health Organization classification recommends the usage of the term sarcomatoid carcinoma (SC) for all biphasic malignant neoplasms of the urinary tract exhibiting morphologic and/or immunohistochemical evidence of epithelial and mesenchymal differentiation. While most SC have been described in the urinary bladder, ureteral SC are extremely rare tumors. Here, we report on the clinical, morphological, and molecular biological findings of two cases in this unusual location. The genetic alterations investigated by comparative genomic hybridization in the epithelial and the mesenchymal component of both cases showed considerable but not complete overlap. Moreover, in spite of many morphological differences between the two cases, both cases shared some genetic gains and losses. Our findings are compatible with the concept that SC originates from a common pluripotent progenitor cell with a potential for epithelial and mesenchymal differentiation.