Congenital Mesoblastic Nephromas with lmmunohistochemical and Flow Cytometric Analysis

ABSTRACT

We reviewed 7 cases of congenital mesoblastic nephroma (4 cases of classical mesoblastic nephroma (CMN) and 3 cases of atypical mesoblastic nephroma (AMN)) using immuno-histochemical and flow cytometric study. Results are as follows. 1) The mean tumor size was 5 (3 to 7cm)cm in CMN and 9 (7 to 10cm)cm in AMN. The AMN revealed hemorrhage and necrosis in two Of three cases. A case of AMN showed cystic change without hemorrhage and necrosis. Mitotic count ranged in 0~4/10HPF in CMN and 20-35/10HPF in AMN. 2) Immunohistochemistry for vimentin was all positive. Actin, desmin were weakly positive in CMN, but negative in AMN. The findings were consistent with myofibroblastic differentiation in CMN and AMN was considered to be the less differentiated form of CMN. 3) Flow cytometiic analysis showed diploidy in two of two CMNs and two of three AMNs. Only one AMN showed aneuploidy with DNA index of 1.41. %SG2M were 8.1 and 15.9 (mean 12.0) in CMN and 16.9, 32.9 and 19.3 (mean 22.9) in AMN, respectively. We concluded that AMN should be distinguished from CMN, clinicopathologically.