ABSTRACT
<p><b>OBJECTIVE</b>To study the morphologic characteristics and immunophenotype of juxtaglomerular cell tumor of the kidney (JGCT), with discussion on its diagnostic clues and possible histogenesis.</p><p><b>METHODS</b>The clinical, pathologic and immunohistochemical features of 5 cases of JGCT were evaluated. In addition, 5 cases of hemangiopericytoma and 5 cases of cutaneous glomus tumor were selected for comparative immunohistochemical analysis.</p><p><b>RESULTS</b>The JGCT cases came from 4 females and 1 male (mean age at diagnosis = 32 years). All of them manifested symptoms of systemic hypertension. Four of the patients received partial nephrectomy and the remaining patient was treated by radial nephrectomy. All of them were followed up for a period of 4 to 66 months (average = 27 months). There was no evidence of local recurrence or distant metastases. On gross examination, these JGCTs were well-circumscribed and situated in the renal cortex and measured 4.4 cm in greatest dimension on average. Histologically, the tumor was characterized by the following three features: (1) solid sheets of relatively uniform polygonal to round cells with lightly eosinophilic cytoplasm, sometimes containing PAS-positive intracytoplasmic granules; (2) absence of or very scanty mitotic figures; (3) interstitium rich in thin-walled capillaries, associated with focal hyaline change and hemangiopericytoma-like architectural pattern. Under electron microscopy, characteristic rhomboid-shaped renin granules were found in the cytoplasm. All JGCTs were immunoreactive for renin, CD34, actin, and calponin. In contrast, all glomus tumors were negative for renin and all hemangiopericytomas were negative for actin.</p><p><b>CONCLUSIONS</b>JGCT is a rare benign renal neoplasm typically found in young adults and manifests as systemic hypertension. The tumor cells may be originated from modified vascular smooth muscle cells. The identification of renin granules by electron microscopy and demonstration of the characteristic immunophenotype is the key to correct pathologic diagnosis.</p>