Congenital Mesoblastic Nephroma Associated with Focal and Segmental Sclerosis

Dr. E.A. Bambirra, Nephropathology Laboratory, Pathology Department, Medical School, Federal University of Minas Gerais (APM), Caixa Postal 340-APM, Belo Horizonte-MG, CEP 30.130-100 (Brazil) Dear Sir, Since the classic study of Bolande et al. [1], congenital mesoblastic nephroma (CMN) has been considered to be an entity separate from Wilms’ tumor. It is a rather unusual neoplasm ofinfancy and early childhood [1-8]. Complete histological investigation is crucial for accurate categorization of CMN and diagnosis of simultaneous underlying kidney pathology. A scan view of the contralateral kidney and a long follow-up definitely contribute to a better understanding of the clinical course of these patients. Though CMN usually occurs in the absence of recognized clinical syndromes, there are some reports showing association of this tumor with hemihypertrophy, polyhydram-nios and hypercalcemia [2, 3]. We describe here an unusual and interesting case of CMN which to our knowledge represents the first documentation of the association of focal segmental sclerosis (FSS) and progressive renal failure. A 7-month-old white normotense male infant, who had a cryptic right testicle, presented a mass in the right flank which was displacing the urether and vena cava. Heterogeneous areas and mi-crocalcifications were observed in the right kidney by computed tomography and ultra-sonography. Urinalysis showed maximum documented proteinuria of 3.4 mg/24 h and no microscopic hematuria. The initial BUN/ creatinine ratio was 10/0.9 mg/lOOml. At the time of nephrectomy the imaging of the left kidney was normal. The patient underwent nephrectomy. The excised kidney weighed 700 g, and measured 16 × 8 cm. The external surface was smooth and pale tan. On the cut surface there was a well-limited mass measuring 12 × 8 × 4 cm. This mass was completely enveloped by a smooth capsule, with a whorled appearance and of fibroelastic consistency (fig. 1). The remaining renal parenchyma surrounding the lesion was normal. Microscopic examination of the tumor mass revealed the pattern of typical CMN, confined to the capsule limits (fig. 2). Histological examination of the remaining kidney parenchyma disclosed areas of focal glomerulo-sclerosis (FGS). One year after surgery, arterial hypertension was detected and poorly controlled. Urinalysis showed maximum documented proteinuria 3.4 mg/24 h, intermittent microscopic hematuria and a serum BUN/creati-nine ratio of 27/10 mg/l00 ml. In November 1993 the patient was 2 years and 8 months old and presented periorbicular edema, a blood pressure of 190/110, and a serum BUN/creatinine ratio of 197/27 mg/l00 ml. At that time the left renal ultrasound