PRIMARY HEPATIC MALIGNANT-TUMOR WITH RHABDOID FEATURES - A HISTOLOGICAL, IMMUNOCYTOCHEMICAL, AND ELECTRON-MICROSCOPIC STUDY OF 4 CASES AND A REVIEW OF THE LITERATURE

Malignant tumors of the liver with rhabdoid features (MTR) are uncommo n: Only 14 previous cases are reported in the literature, These tumors are characterised morphologically by sheets of large polygonal cells with abundant eosinophilic cytoplasm containing a, periodic acid Schif f's-positive hyaline globular inclusion and vesicular nuclei with a ce ntral prominent nucleolus. Immunohistochemically, the inclusions al le ast shaw positivity for vimentin and epithelial markers and sometimes for other antigens. Ultrastructurally, the inclusions are composed of whorled intermediate filaments. Despite the superficial resemblance to cells of muscle origin implied in the term rhabdoid, there is no immu nohistochemical or ultrastructural evidence to support such a derivati on. We describe four additional children with tumors of this type, in three of whom tumor cells showed focal membrane positivity for MIC-2 o n immunostaining. Its expression in an hepatic MTR may indicate neuroe pithelial differentiation. Hepatic MTR should be considered in the dif ferential diagnosis of an undifferentiated primary liver tumor in an i nfant in whom the alpha-fetoprotein concentration is normal or only sl ightly elevated for age.