Anaplastic Large-Cell Lymphoma (Ki-1 Lymphoma) and Diffuse Large-Cell Immunoblastic Lymphoma: Two Diagnostic Problem Cases

Electron microscopy can be used to establish diagnoses in some otherwise difficult cases of neoplasia, but it is not generally regarded as important in the diagnosis of lymphoma. However, in some cases of anaplastic tumors not initially recognized as lymphomas, electron microscopy can prove quite valuable. Two cases are reported in which lymphoma was not suspected on the basis of the histologic findings, but was diagnosed by electron microscopy. Case 1 involved a 60-year-old woman who presented with a retroperitoneal mass that was located primarily in the body of the psoas muscle. Nuclear pockets were seen with electron microscopy. Ultimately she was diagnosed with anaplastic large-cell lymphoma (Ki-1 lymphoma). Case 2 involved a 43-year-old male with retroperitoneal lymphadenopathy, renal failure, polyclonal gammopathy, and a febrile illness. Signet-ring cells without junctions were identified with electron microscopy. Immunoperoxidase stains confirmed diffuse large-cell immunoblastic lymphoma.