Recurrent and metastatic congenital mesoblastic nephroma: where does the evidence stand?

Fifty years ago, Bolande described Congenital Mesoblastic Nephroma (CMN) as a benign lesion. Unexpected aggressive clinical behaviors prompted a sub-classification based on histology. Recent molecular genetic evidence has identified the aggressive cellular variant to be the renal manifestation of congenital infantile fibrosarcoma. We submit a reappraisal and analysis of the available literature on recurrent and metastatic CMN. An electronic search of PubMed, MEDLINE, EMBASE, and Scopus yielded 38 children with local recurrence and/or metastases. Of the 38 children with local recurrence and/or metastasis, 59% were girls. Median time to recurrence was 6 months (range 1-12 months). The commonest sites of metastases were the lung (39%) and liver (29%). Fifty percent of these children died of disease. The outcome of additional chemotherapy (p = 0.5) did not differ from that of surgery alone. The choice of chemotherapy did not influence the outcome (p = 0.6). Recurrence and metastasis in cellular CMN are much more common than described earlier and carry a high mortality. Children with cellular and mixed CMN require close clinical and radiological follow-up for a minimum of 12 months after primary surgery. Surgery is the mainstay of the treatment of recurrent and metastatic lesions. Neoadjuvant chemotherapy is recommended only if the lesion is inoperable. Targeted therapy may be an option in treatment of refractory cases.