Juxtaglomerular cell tumor of the kidney: case report and differential diagnosis with emphasis on pathologic and cytopathologic features.

This study presents a case of juxtaglomerular cell tumor (JCT) in a 12-year-old girl with hypertension. Fine needle aspirate (FNA) cytology demonstrated a neoplasm with features of a papillary carcinoma, prompting a right radical nephrectomy. Histological examination revealed solid sheets of round epithelioid cells with eosinophilic granular cytoplasm, and distinct cell borders in a background of widespread hemorrhage. Electron microscopy revealed cytoplasmic renin granules. The differential diagnosis of a renal mass in a young patient with hypertension includes JCT, Wilm's tumor, and renal cell carcinoma, which may produce renin. The renin granules detected by electron microscopy are characteristic of JCT, and the diagnosis is confirmed by ultrastructural study. FNA cytology is not sensitive enough for the diagnosis of JCT and its results must be carefully interpreted.