Calcification and ossification in a congenital mesoblastic nephroma

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.

Cellular mesoblastic nephroma (infantile renal fibrosarcoma): institutional review of the clinical, diagnostic imaging, and pathologic features of a distinctive neoplasm of infancy

BACKGROUND

Cellular mesoblastic nephroma has been associated with a more aggressive course than classic mesoblastic nephroma, including local recurrences and metastases.

OBJECTIVE

To define the clinicopathologic and imaging features distinguishing cellular from classic mesoblastic nephroma.

MATERIALS AND METHODS

Retrospective review of clinical charts and imaging studies of ten children with mesoblastic nephroma from 1996 to 2007 at a large children's hospital.

RESULTS

In six children the mesoblastic nephroma was pure cellular, in two mixed, and in two classic. The mean ages at diagnosis were 107 days for those with the cellular form, and 32 days for those with the classic form. Hypoechoic or low-attenuation regions representing necrosis or hemorrhage were found in all children with the cellular form and in none of those with the classic form. Hypertension was present in 70% and hypercalcemia in 20% of the children and resolved following nephrectomy. Two cellular tumors encased major abdominal vessels. Local recurrence and metastases occurred within 6 months of tumor resection in two children with the cellular form. Intraspinal extension and intratumoral pseudoaneurysm were seen in one child with the cellular form. The cellular tumors shared histopathologic features with infantile fibrosarcoma (IFS), and RT-PCR testing in two children with the cellular form revealed the t(12;15) ETV6-NTRK3 gene fusion common to IFS.

CONCLUSION

Distinct from the classic form, cellular mesoblastic nephroma is more heterogeneous in appearance on imaging, tends to be larger and present later in infancy, and can exhibit aggressive behavior including vascular encasement and metastasis. Intraspinal extension and intratumoral pseudoaneurysm are previously unreported findings encountered in our cellular mesoblastic nephroma series. The shared histopathology and translocation gene fusion support the concept of cellular mesoblastic nephroma as the renal form of IFS.

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.