"Anemone" cell (villiform) tumors: electron microscopy and immunohistochemistry of five cases.

Five large cell malignant neoplasms were studied by immunohistochemistry and electron microscopy. Ultrastructural examination demonstrated numerous circumferential microvilli in 3 cases and a more polarized distribution in 2 cases. The tumor cells in 2 cases demonstrated the surface glycoprotein T29/33, indicative of a hematopoietic neoplasm. Two cases (including one positive for T29/33) contained intracytoplasmic IgG-kappa. Anti-keratin staining using both polyclonal and monoclonal antibodies was negative. Two patients are alive and in remission after treatment for lymphoma. One died with tumor following a progressive course, and one has been lost to follow-up. A fifth patient died of tumor and at autopsy was found to have a disseminated pancreatic tumor. Microvilli around large malignant cells have been commonly associated with epithelial tumors; however, our findings indicate that, in the absence of intercellular junctions and tonofilaments, the possibility of malignant lymphoma should be considered and pursued immunohistochemistry.