[Mucinous spindle cell carcinoma of the kidney. A molecular analysis]

The new WHO-classification of renal tumors includes new subtypes, one of which is the mucinous, tubular, and spindle cell carcinoma. Many of these tumors had been previously diagnosed as sarcomatoid carcinoma. There are areas of cord-like growth and spindle cell configuration, sometimes with a clear cell appearance. The cells have low-grade nuclear features. It has been postulated that these tumors are related to the loop of Henle. In this study, 21 tumors were immunohistochemically and genetically analyzed. The analysis showed complex genomic aberrations, but no chromosome 3p losses. Fluorescence in situ hybridization detected no von Hippel-Lindau gene deletions on chromosome 3p25, which are characteristic for clear cell renal carcinomas. These findings show that there is no genetic relationship to clear cell renal carcinomas. The results of the immunohistochemical analyses showed a complex immunophenotype, but could not prove a derivation from the loop of Henle. The prognosis of these tumors seems to be favorable.