Fourteen renal tumors other than renal cell carcinomas were studied in order to determine their sonographic characteristics.
Histologically, the tumors were 11 benign tumors (8 angiomyolipomas, 2 oncocytomas, and 1 multilocular cystic nephroma)
and 3 malignant tumors (1 Wilms' tumor, 1 primitive neuroectodermal tumor, and 1 chromophobe cell renal carcinoma).
Sonographic stage was higher in the malignant than in the benign tumors. Internal echo patterns of the malignant tumors were
more heterogeneous than those of benign tumors. One angiomyolipoma produced a homogeneously isoechoic pattern that
mimicked that of a renal cell carcinoma; this pattern was probably caused by histologic predominance of myomatous
components. Although multilocular cystic nephroma is said to exhibit a mutiloculated anechoic or hypoechoic pattern, the
cystic nephroma studied here produced a homogeneously hyperechoic pattern, which we would presume to have been caused by
a histologic structure of grouped microcysts. The primitive neuroectodermal tumor and chromophobe cell renal carcinoma had
almost homogeneous echotextures, probably because they had a uniform growth pattern of tumor cells and lacked massive
hemorrhages or necroses.