Clear cell sarcoma of the kidney is a distinct, highly malignant pediatric
neoplasm. Its occurrence in adults is extremely rare and the subject of isolated case reports. We present a series of four cases (three males and one female) identified in an adolescent and in young adults (16, 18, 20, and 25 years) with flank mass (three cases),
hematuria (two cases),
flank pain (two cases), and
hypertension (one case). Three patients had stage III disease and one had stage I disease (National
Wilms' Tumor Study staging system). All
tumors had predominantly or exclusively the classic histology of a monotonous proliferation of uniform small round cells with evenly distributed fine
chromatin, although focal microcyst formation (two cases) and spindled architecture (one case) (variant patterns) were also noted.
Therapy in all cases consisted of surgery and
chemotherapy with or without radiation. Follow-up data (29-202 months) showed distant
metastases in all four cases, including the lung (four cases), bone (two cases), and the liver (two cases). Three patients died of disease at 29, 59, and 63 months (mean, 50.3 months), and one patient is alive with no evidence of disease at 202 months. Ultrastructural features included scattered primitive junctions, short and irregular cytoplasmic extensions, and scant to a moderate amount of mitochondria. Immunohistochemical study (three cases) showed immunoreactivity with
vimentin (two cases) and no reaction with
cytokeratin,
epithelial membrane antigen,
S-100 protein, or
desmin. Flow cytometric analysis showed diploid
DNA content in three primary
tumors and
tetraploidy in one metastatic
tumor. The proliferative activity (S-phase fraction) was low to intermediate (mean, 9.8%). Our data suggest that
clear cell sarcoma of the kidney in the young adult age group resembles its pediatric counterpart in ultrastructural and immunohistochemical characteristics, proclivity for skeletal and visceral
metastasis,
DNA diploid status with relatively low S-phase, and aggressive
clinical course.
Clear cell sarcoma of the kidney in adult patients, although rare, must be differentiated from sarcomatoid
carcinoma,
sarcomas, and round cell
tumors because of its unique characteristics in comparison to other
renal neoplasms.