Vimentin is currently used to differentiate between malignant
renal carcinomas and benign oncocytomas. Recent reports showing
Vimentin positive oncocytomas seriously question the validity of this present diagnostic approach.
Vimentin 3 is a spliced variant and ends with a unique C-terminal ending after exon 7 which differentiates it from the full length version that has 9 exons. Therefore, the
protein size is different; the full length
Vimentin version has a
protein size of ~57 kDa and the truncated version of ~47 kDa. We designed an antibody, called Vim3, against the unique C-terminal ending of the
Vimentin 3 variant. Using immune histology, immune fluorescence, Western blot, and qRT-PCR analysis, a Vim3 overexpression was detectable exclusively in
oncocytoma, making the detection of Vim3 a potential specific marker for benign kidney
tumors. This antibody is the first to clearly differentiate benign
oncocytoma and the mimicking eosinophilic variants of the RCCs. This differentiation between malignant and benign RCCs is essential for operative planning, follow-up
therapy, and patients' survival. In the future the usage of
Vimentin antibodies in routine pathology has to be applied with care. Consideration must be given to
Vimentin specific binding
epitopes otherwise a misdiagnosis of the patients'
tumor samples may result.