Atypical Mesoblastic Nephroma: A case report

ABSTRACT

Congenital mesoblastic nephroma (CMN) is generally considered to be a rare benign renal tumor in neonates, requiring only total excision. However, an atypical mesoblastic nephroma (AMN) may behave aggressively, in contrast to a congenital mesoblastic nephroma. AMN shows atypical gross and microscopic features such as hemorrhage, necrosis, high cellularity, and a mitotic index. We report a case of atypical mesoblastic nephroma which presented in a 2 month-old male infant. Grossly, the tumor involved the upper and the midportion of the left kidney. On section, the cut surface was flesh,which was hemorrhagic necrotic, multicystic degenerative, grayish-white, and heterogenous. Microscopically, the tumor showed a high degree of cellularity and an arrangement of monophagic ovoid spindle cells in sheets and vague interlacing bundles. The individual tumor cells showed fusiform to oval nuclei, indistinct scanty pale-eosinophilic cytoplasm, and many mitotic features.