Diagnostic and therapeutic problems posed by malignant non Hodgkin lymphoma of renal origin in children. Apropos of 7 cases]

BACKGROUND. The kidneys of non Hodgkin lymphoma patients frequently contain lymphoma cells, but these tumors rarely arise in the renal tissue and are rarely located there. PATIENTS. A diagnosis of non Hodgkin lymphoma of renal origin or predominantly located in kidneys was made in 7 patients aged 2-14 years old. These patients formed part of a total of 450 patients with non Hodgkin lymphomas seen from 1974 to 1987. The first manifestation in these 7 children was an abdominal mass associated with hypertension in 3 cases; 2 of whom presented with acute kidney failure. Ultrasonography showed hypoechogenous masses in one (2 cases) or both kidneys (5 cases). The diagnosis of malignant lymphoma was made directly in only one patient who also presented with mediastinal and abdominal lymph node enlargement. In the others, the first diagnosis was Wilms tumor (5 cases) and polycystic disease of the kidney (1 case); the correct diagnosis of malignant lymphoma was later made from biopsies of renal (4 patients) or extrarenal involved tissue (2 patients). Six of the 7 cases were Burkitt lymphomas, and all 7 were in stage III (3 patients) and IV (4 patients). 6 patients (3 stage III and 3 stage IV) were successfully treated by chemotherapy with a median follow-up of 9 years. CONCLUSIONS. Differential diagnosis between non Hodgkin lymphomas of renal origin and a Wilms tumor may be difficult even though kidney failure is more frequent in lymphoma. Sonography is the best method for diagnosis showing typical hypoechogenous masses and diffuse homogeneous infiltration of the kidneys. In the absence of extrarenal (meningeal, testis, bone marrow) dissemination, definite evidence of lymphoma depends on the histological examination of tumoral tissue obtained by surgical biopsy.