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Ossifying Renal Tumor of Infancy
0022-5347/93/1495-1080$03.00/0 Vol. 149, 1080-1081, May 1993
THE JOURNAL OF UROLOGY
Copyright © 1993 by AMERICAN UROLOGICAL ASSOCIATION, INC.
Printed in U. S. A.
OSSIFYING RENAL TUMOR OF INFANCY J. STEFFENS, J. KRAUS, B. MISRO, S. ALLOUSSI, K. REMBERGER, R. U. BRAEDEL, M. GIRMANN AND M. ZIEGLER From the Departments of Urology, Pathology and Radiology, University of Saarland, Homburg and Department of Pediatrics, Children's Hospital of Saarland, Neunkirchen Kohlhof, Germany
ABSTRACT
Ossifying renal tumor of infancy is a rare but distinctive tumor that presents as a mass in the pelvicaliceal system. It is usually suspected to be a calculus until surgical exploration reveals dense tumor attachment to the renal parenchyma. The histogenesis of this lesion has not been established. We present a case of this unusual neoplasm. A renal sparing procedure was performed on this biologically benign tumor. Followup after 20 months showed no evidence of recurrence. KEY WORDS:
kidney neoplasms; ossification, pathologic; kidney pelvis; infant
The most common renal tumors in infancy are mesoblastic nephroma, nephroblastoma and precursors of classical Wilms tumor, such as nodular renal blastema and nephroblastomatosis.1-3 These lesions arise from renal blastema. We describe a tumor with a different presentation and localization but with similar histological features to Wilms tumor and its precursors. CASE HISTORY
An ll-month-old white girl without urogenital or other malformations was hospitalized after 2 episodes of painless macroscopic hematuria. She had no fever or hypertension, and had normal blood parameters. Sonography revealed typical stone shadows in the renal pelvis and collecting system of the left kidney resembling a staghorn calculus. The renal parenchyma was normal. A roentgenogram without contrast medium revealed no renal stone formations. An excretory urogram showed a filling defect of the left renal pelvis and calices (fig. 1). Computerized tomography revealed a hyperdense, calcified, noninvasive mass in the renal pelvis without enhancement of contrast medium (fig. 2). Renal arteriography was normal and showed no evidence of tumor. At renal exploration a hard mass was palpable within the renal pelvis. The renal parenchyma was normal. Initial diagnosis was a renal staghorn stone and pyelotomy was performed. Intraoperatively, a strong, white mass was found and believed to be a rare tumor. Total extraction was possible with 2 additional upper and lower calicotomies. Cross section of the mass showed a solid homogeneous white tumor. Histological and immunohistological investigations confirmed an ossifying renal tumor (fig. 3). Convalescence was uneventful and the patient was discharged from the hospital 10 days postoperatively. Careful nephrosonographic examinations were performed monthly and at 20 months there was no recurrence. DISCUSSION
We add another case to the short list of a rare but distinctive renal tumor occurring in the first year of life.4-9 The calcified lesion usually presents as a radiopaque mass in the renal collecting system and can be incorrectly diagnosed as a calculus. 4-8 Surgical exploration often reveals dense tumor attachment to the renal parenchyma and the correct diagnosis can only be established postoperatively. The histological features of ossifying tumors observed by Beckwith in the extensive material of the National Wilms Tumor Study showed spindle cell components in nearly all cases but apparently unequivocal intralobular nephrogenic rests in only 1.8 Our patient also had nephrogenic rests, which led us initially to consider this lesion to be nephroblastomatosis. Accepted for publication October 30, 1992.
FIG. 1. Excretory urogram shows filling defect of left renal pelvis and calices.
The histogenesis of these tumors remains unclear. The primary localization in the renal collecting system, the known occurrence of ossification in some urothelial tumors, and the rare occurrence of osteosarcomas in the adult kidney and urinary tract indicate that these tumors derive from urothelium rather than from the metanephros. 5 It appears that the lesion is biologically benign because none of the reported and unpublished cases is known to have recurred or metastasized. 4- 9 In contrast to the previous reports, we did not perform nephrectomy or initiate radiotherapy or chemotherapy to treat our
1080
1081
OSSIFYING RENAL TUMOR Of INFANCY
patient successfully.4-7,9 Complete extraction of the calcified mass was performed, since the correct diagnosis of the tumor had not been determined at operation, Monthly sonographic monitoring is done because the risk remains for development of a malignant tumor. At 20 months there was no evidence of recurrence or spread of this tumor. Macroscopic hematuria was the principal indicator in all of the reported cases and this should always be evaluated carefully to determine the etiology. Although anatomical malformations, stones, infections and trauma are the main causes of hematuria in infancy, the presence of a tumor must also be excluded. In summary, a renal sparing operation with complete enucleation of the tumor is recommended as appropriate treatment of ossifying renal tumors. Careful followup of the children is important.
Dr. J. B. Beckwith contributed to the diagnosis of this case. FIG. 2. Computerized tomography shows hyperdense. calcified, noninvasive mass in renal pelvis without enhancement of contrast medium. REFERENCES
FIG. 3. Histologically, tumor consisted mainly of dense osteoid-like matrix with poor cellularity (left side). Sparse spindle-cell component with tubular structures was also present (lower right side). H & E, reduced from x50.
1. Bolande, R. P.: Congenital and infantile neoplasia of the kidney. Lancet, 2: 1497, 1974. 2. Beckwith, J. B.: Renal neoplasms of childhood. In: Diagnostic Surgical Pathology. Edited by S. S. Sternberg. New York: Raven Press, vol. 2, chapt. 39, pp. 1331-1353, 1989. 3. Bove, K. E., Koffler, H. and McAdams, A. J.: Nodular renal blastema. Definition and possible significance. Cancer, 24: 323, 1969. 4. Kiiss, R: Un cas de nephroblastome calcifie simulant un calcul. J. d'Urol. Nephrol., 73: 653, 1967. 5. Chatten, J., Cromie, W. J. and Duckett, J. W.: Ossifying tumor of infantile kidney: report of two cases. Cancer, 45: 609, 1980. 6. Fernbach, S. K., Schlesinger, A. E. and Gonzalez-Crussi, F.: Calcification and ossification in a congenital mesoblastic nephroma. Urol. Rad., 7: 165, 1985. 7. Jerkins, G. R and Callihan, T. R: Ossifying renal tumor of infancy. J. Urol., 135: 120, 1986. 8. Beckwith, J. B.: Personal communication. 9. Middlebrook, P. F., Jimenez, C. L. and Schillinger, J. F.: Ossifying renal tumor of infancy: a case report. J. Urol., 147: 1337, 1992.
i I
THE JOURNAL OF UROLOGY
Copyright © 1993 by AMERICAN UROLOGICAL ASSOCIATION, INC.
Printed in U. S. A.
OSSIFYING RENAL TUMOR OF INFANCY J. STEFFENS, J. KRAUS, B. MISRO, S. ALLOUSSI, K. REMBERGER, R. U. BRAEDEL, M. GIRMANN AND M. ZIEGLER From the Departments of Urology, Pathology and Radiology, University of Saarland, Homburg and Department of Pediatrics, Children's Hospital of Saarland, Neunkirchen Kohlhof, Germany
ABSTRACT
Ossifying renal tumor of infancy is a rare but distinctive tumor that presents as a mass in the pelvicaliceal system. It is usually suspected to be a calculus until surgical exploration reveals dense tumor attachment to the renal parenchyma. The histogenesis of this lesion has not been established. We present a case of this unusual neoplasm. A renal sparing procedure was performed on this biologically benign tumor. Followup after 20 months showed no evidence of recurrence. KEY WORDS:
kidney neoplasms; ossification, pathologic; kidney pelvis; infant
The most common renal tumors in infancy are mesoblastic nephroma, nephroblastoma and precursors of classical Wilms tumor, such as nodular renal blastema and nephroblastomatosis.1-3 These lesions arise from renal blastema. We describe a tumor with a different presentation and localization but with similar histological features to Wilms tumor and its precursors. CASE HISTORY
An ll-month-old white girl without urogenital or other malformations was hospitalized after 2 episodes of painless macroscopic hematuria. She had no fever or hypertension, and had normal blood parameters. Sonography revealed typical stone shadows in the renal pelvis and collecting system of the left kidney resembling a staghorn calculus. The renal parenchyma was normal. A roentgenogram without contrast medium revealed no renal stone formations. An excretory urogram showed a filling defect of the left renal pelvis and calices (fig. 1). Computerized tomography revealed a hyperdense, calcified, noninvasive mass in the renal pelvis without enhancement of contrast medium (fig. 2). Renal arteriography was normal and showed no evidence of tumor. At renal exploration a hard mass was palpable within the renal pelvis. The renal parenchyma was normal. Initial diagnosis was a renal staghorn stone and pyelotomy was performed. Intraoperatively, a strong, white mass was found and believed to be a rare tumor. Total extraction was possible with 2 additional upper and lower calicotomies. Cross section of the mass showed a solid homogeneous white tumor. Histological and immunohistological investigations confirmed an ossifying renal tumor (fig. 3). Convalescence was uneventful and the patient was discharged from the hospital 10 days postoperatively. Careful nephrosonographic examinations were performed monthly and at 20 months there was no recurrence. DISCUSSION
We add another case to the short list of a rare but distinctive renal tumor occurring in the first year of life.4-9 The calcified lesion usually presents as a radiopaque mass in the renal collecting system and can be incorrectly diagnosed as a calculus. 4-8 Surgical exploration often reveals dense tumor attachment to the renal parenchyma and the correct diagnosis can only be established postoperatively. The histological features of ossifying tumors observed by Beckwith in the extensive material of the National Wilms Tumor Study showed spindle cell components in nearly all cases but apparently unequivocal intralobular nephrogenic rests in only 1.8 Our patient also had nephrogenic rests, which led us initially to consider this lesion to be nephroblastomatosis. Accepted for publication October 30, 1992.
FIG. 1. Excretory urogram shows filling defect of left renal pelvis and calices.
The histogenesis of these tumors remains unclear. The primary localization in the renal collecting system, the known occurrence of ossification in some urothelial tumors, and the rare occurrence of osteosarcomas in the adult kidney and urinary tract indicate that these tumors derive from urothelium rather than from the metanephros. 5 It appears that the lesion is biologically benign because none of the reported and unpublished cases is known to have recurred or metastasized. 4- 9 In contrast to the previous reports, we did not perform nephrectomy or initiate radiotherapy or chemotherapy to treat our
1080
1081
OSSIFYING RENAL TUMOR Of INFANCY
patient successfully.4-7,9 Complete extraction of the calcified mass was performed, since the correct diagnosis of the tumor had not been determined at operation, Monthly sonographic monitoring is done because the risk remains for development of a malignant tumor. At 20 months there was no evidence of recurrence or spread of this tumor. Macroscopic hematuria was the principal indicator in all of the reported cases and this should always be evaluated carefully to determine the etiology. Although anatomical malformations, stones, infections and trauma are the main causes of hematuria in infancy, the presence of a tumor must also be excluded. In summary, a renal sparing operation with complete enucleation of the tumor is recommended as appropriate treatment of ossifying renal tumors. Careful followup of the children is important.
Dr. J. B. Beckwith contributed to the diagnosis of this case. FIG. 2. Computerized tomography shows hyperdense. calcified, noninvasive mass in renal pelvis without enhancement of contrast medium. REFERENCES
FIG. 3. Histologically, tumor consisted mainly of dense osteoid-like matrix with poor cellularity (left side). Sparse spindle-cell component with tubular structures was also present (lower right side). H & E, reduced from x50.
1. Bolande, R. P.: Congenital and infantile neoplasia of the kidney. Lancet, 2: 1497, 1974. 2. Beckwith, J. B.: Renal neoplasms of childhood. In: Diagnostic Surgical Pathology. Edited by S. S. Sternberg. New York: Raven Press, vol. 2, chapt. 39, pp. 1331-1353, 1989. 3. Bove, K. E., Koffler, H. and McAdams, A. J.: Nodular renal blastema. Definition and possible significance. Cancer, 24: 323, 1969. 4. Kiiss, R: Un cas de nephroblastome calcifie simulant un calcul. J. d'Urol. Nephrol., 73: 653, 1967. 5. Chatten, J., Cromie, W. J. and Duckett, J. W.: Ossifying tumor of infantile kidney: report of two cases. Cancer, 45: 609, 1980. 6. Fernbach, S. K., Schlesinger, A. E. and Gonzalez-Crussi, F.: Calcification and ossification in a congenital mesoblastic nephroma. Urol. Rad., 7: 165, 1985. 7. Jerkins, G. R and Callihan, T. R: Ossifying renal tumor of infancy. J. Urol., 135: 120, 1986. 8. Beckwith, J. B.: Personal communication. 9. Middlebrook, P. F., Jimenez, C. L. and Schillinger, J. F.: Ossifying renal tumor of infancy: a case report. J. Urol., 147: 1337, 1992.
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