抄録
A grayish white nodule, 1.0 × 1.0 × 2.0 cm in size, was grossly observed in the liver of a 110-week-old male CD-1 mouse. Microscopically, the lesion was characterized by two types of proliferation area, one of which was composed of a lipomatous proliferation with small spindle cells and severe extramedullary hematopoiesis (EMH). The other area was composed of large spindle cells closely proliferating along the hepatic cords. The proliferative lesion was partly positive for vimentin and had increased amounts of laminin, which is an extracellular matrix protein synthesized by Ito cells. Ultrastructurally, the lipomatous area contained cells with individual lipid droplets in the cytoplasm. The characteristic findings of this nodule were similar to those of Ito cell tumors in mice reported previously, except for the severe EMH in our case.
