Ossifying renal tumor of infancy: a case report

Ossifying renal tumor of infancy: a case report

Ossifying renal tumor of infancy (ORTI) is an extremely rare benign renal solid tumor with typical clinical and pathological features. Most cases are diagnosed in infants that are less than 12 months of age and is more common in males. The first symptom in most patients is painless gross hematuria. Microscopically, the tumor has three main components: an osteoid core, osteoblast-like cells, and spindle cells. We reported a case of a 21-day-old patient diagnosed with ORTI who underwent partial nephrectomy and had good follow-up. The unique features of this case are the strong expression of Wilms Tumor-1 (WT-1) and a high Ki-67 index in the hot spot area. ORTI is considered to have a favorable prognosis. Due to the rarity of WT-1 positivity and high Ki-67 index, we should be highly aware that this patient needs to be followed closely. In addition, we reviewed the available literature on ORTI, with the aim of summarizing the diagnostic and therapeutic experience. The diagnosis needs to be given cautiously on the basis of clinical symptoms, imaging, and pathologic examination. Depending on the location and extent of the tumor, surgery can be performed by partial nephrectomy or nephrectomy to avoid overtreatment.

Case report and literature review of a rare diagnosis of ossifying renal tumour of infancy

One must entertain a broad differential diagnosis for infants presenting with gross hematuria. Initial workup includes urine analysis, serum laboratory values and abdominal ultrasound. We describe an infant presenting with gross hematuria found to have a calcified renal mass upon initial ultrasound and subsequent computed tomography scan. We considered a differential diagnosis of, but not exclusive to, staghorn calculi, nephroblastoma, Wilms' tumour, mesoblastic nephroma and ossifying renal tumour of infancy (ORTI). A nephrectomy was performed, and the pathology report identified the calcified mass as an ORTI.

Ossifying renal tumor of infancy (ORTI): a case report and review of the literature

We present the case of a 6-month-old boy who was referred to us with the chief complaint of intermittent painless gross hematuria. Computed tomography (CT) scan of the abdomen showed a partially calcified soft-tissue mass that was located in the lower pole of the right kidney and extended into the collecting system. Consequently, a partial nephrectomy was performed. The resected specimen showed that the tumor was partially calcified and occupied the renal pelvis. The histological findings suggested a diagnosis of ossifying renal tumor of infancy (ORTI), only 16 cases of which have been reported in the literature. The pathogenesis of this condition has not been well established. ORTI should be considered in the differential diagnosis for infants with gross hematuria and a calcified mass in the pelvicalyceal system.

Ossifying renal tumor of infancy

A renal ossifying tumor of infancy is a rare event with few cases having been published, and the etiology has not yet been established. We report on two new cases of this unusual neoplasm. A 2-year-old boy presented with intermittent painless gross hematuria. After several diagnostic procedures, an open pyelolithotomy was performed and the histological diagnosis of renal tumor of infancy was finally made. The history of the second case is very similar. An 8-week-old infant presented with gross hematuria. As in the first case, an open pyelolithotomy was performed and a tumor entirely covered with blood clots was found in the renal pelvis and completely removed. A histological diagnosis of renal ossifying tumor of infancy was made. Using the literature available, the histological criteria and biological behavior are discussed, together with the diagnostic and therapeutic algorithm for this tumor. In infants with gross hematuria and a calcified (non-)invasive mass in the pelvi-calceal system, renal ossifying tumor should be considered in the differential diagnosis. MRI or CT scan offers a good diagnostic guide.

Ossifying renal tumor of infancy: the first Japanese case with long-term follow-up

Presented is the first Japanese case of ossifying renal tumor of infancy (ORTI), which is an extremely rare tumor and of which only nine cases have been reported in the literature. The patient was a four-month-old Japanese boy presenting as hematuria. A small nodular tumor (approximately 1 cm in size) protruded into the right pelvis from the superior caliceal region. Histologically the tumor originated from the tip of one medullary papilla and consisted of small rounded cells with a dense arrangement and several foci of minimally calcified osteoid lesions, including fewer but larger cells. Transition from the small to larger cells was suggested. The small cell only expressed vimentin, but the larger coexpressed vimentin, desmin, and epithelial membrane antigen. These findings suggested that the small cells differentiated to the larger cells with an epithelial nature associated somehow with osteoid formation. Embryonal metaplasia was assumed to occur in the collecting ducts entrapped by the tumor. The patient has been well without recurrence for more than 23 years. This is the longest survival period compared with other reported cases and confirms the benign nature of ORTI. It is absolutely crucial to make an accurate diagnosis of ORTI to avoid unnecessary treatment.

Ossifying renal tumor of infancy: a clinicopathologic study of nine cases

We studied nine ossifying renal tumors of infancy (ORTI), including all five previously reported cases. There were eight boys and one girl ranging in age from 6 days to 14 months. Gross hematuria was the presenting sign in all nine patients. Eight tumors arose in the left kidney and six in the upper pole. All seven patients with follow-up information were free of recurrence. All lesions were attached to a renal papilla and presented mainly within the calyceal lumen. Two resembled staghorn calculi clinically. All tumors contained varying proportions of osteoid, osteoblastic cells, and spindle cells. The spindle cell component had features strongly suggesting that they represented hyperplastic intralobar nephrogenic rests (ILNR). The proportion of osteoid and degree of osseous maturation increased with increasing age of the patient. ORTI is a distinctive clinicopathologic entity, possibly representing a distinctive interaction between ILNR in the renal papilla with distal collecting duct or urothelial cells in the developing kidney.

Ossifying renal tumor of infancy

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.