Congenital Mesoblastic Nephroma
Congenital mesoblastic nephroma is a low-grade fibroblastic neoplasm arising in the renal sinus of children.
It comprises 5% of pediatric renal neoplasms.
It is the most common kidney tumor in the first 3 months of life and is uncommon after 6 months.
There is no gender predominance.
They are located in the renal sinus.
The treatment of choice is surgical excision.
Mesoblastic nephroma is a low-grade neoplasm; it has infiltrative borders which must be studied carefully because the risk of recurrence appears to be dependent upon the completeness of the resection (Furtwaengler et al. 2006). Only rare cases with hematogeneous metastases have been reported, which are treated with chemotherapy (Loeb et al. 2002).
Grossly this neoplasm is usually large, and its cut surface resembles that of a leiomyoma (firm, whorled or trabeculated, and light colored). The tumor is not encapsulated and typically interdigitated with the surrounding renal parenchyma.
These tumors are frequently immunoreactive for actin with infrequent desmin labeling; CD34 is negative.
Cellular congenital mesoblastic nephroma harbors a specific chromosome translocation, t(12,15), which results in the fusion of the ETV6 and NTRK3 genes (El Demellawy et al. 2016). The gene fusion has not been found in the classic variant.