Rearrangements of 3q were found in 10% of a series of 230 cases of renal cell carcinoma (RCC). Together with observations from the literature, these structural changes can be concluded to involve two different regions, 3q21 and 3q11-12, and are usually present as unbalanced translocations. In some of these cases of RCC with the translocation, the normal chromosome 3 may reduplicate, giving rise to a partial trisomy 3q instead of a partial monosomy 3. In those cases, however, histology shows chromophilic-papillary RCC instead of clear cell-nonpapillary. Hence, besides the still unresolved underlying molecular changes causing RCC, histology may in part depend on the presence of partial monosomy or partial trisomy 3.