[2] Congenital Mesoblastic nephroma is a malignant tumorous growth of the kidney's mesenchyme (i.e. connective tissue cells).

Either event can drive the malignant growth of cells but in most cases the chimeric protein's tyrosine kinase activity appears responsible for doing so.

This suggests that expression of this fused gene may be more common in cellar and mixed mesoblastic nephroma than previously appreciated.

Diagnosis of mesoblastic nephroma and its particular type (i.e. classic, mixed, or cellular) is made by histological examination of tissues obtained at surgery.

[citation needed] Besides its histological appearance, various features of this disease aid in making a differential diagnosis that distinguish it from the following childhood neoplasms: Based on a survey of >800, surgical removal of the entire involved kidney plus the peri-renal fat appeared curative for the majority of all types of mesoblastic nephroma; the patient overall survival rate was 94%.

[2] Removal of the entire afflicted kidney plus the peri-renal fat appears critical to avoiding local recurrences.

Relevant to this issue, a 16-month-old girl with infantile fibrosarcoma harboring the ETV6–NTRK3 fusion gene was successfully treated with larotrectinib.