Fine needle aspiration cytology of mesoblastic nephroma. A case report.

A case of congenital mesoblastic nephroma of the left kidney was diagnosed in a 4-month-old child by fine needle aspiration cytology. The smears consisted of clustered and dyshesive spindle cells with minimal nuclear atypia and mitosis. No epithelial, tubular or glomeruloid differentiation was noted. Considering the age and cytomorphology, a diagnosis of mesoblastic nephroma was made. Histopathology of the nephrectomy specimen showed a tumor with features of atypical mesoblastic nephroma. Cytologic diagnosis of mesoblastic nephroma is important because the tumor has an excellent prognosis, and unlike Wilms' tumor, requires only surgery.