Seventy cases of anaplastic thyroid carcinomas studied at the Universities of Florence (Italy) and Minnesota are presented. Three morphologic patterns were seen: spindle, giant cell, and squamoid, sometimes in combination. Ultrastructurally, evidence of epithelial differentiation was seen in most but not all cases studied. Immunohistochemically, a stain for cytokeratin using a monoclonal antibody was found the most useful adjunct to diagnosis. Unexpected positivity for carcinoembryonic antigen (CEA) was found in several squamoid tumors. The alleged frequent positivity of this tumor type for thyroglobulin and calcitonin was not confirmed. A third of the tumors were associated with a better differentiated component, of which, presumably, they represented a dedifferentiation. The extremely aggressive behavior of anaplastic thyroid carcinomas was confirmed amply in this series: all of the patients in whom follow-up information was available died of their tumor. Small cell tumors should not be included into the anaplastic category, since they invariably belong to other groups, i.e., malignant lymphoma, medullary carcinoma, and poorly differentiated ("insular") carcinoma.
Recently, the morphologic, immunologic, and molecular makeup of a new virus designated human herpesvirus-6 (HHV-6) has been described. Because cell cultures of HHV-6-infected mononuclear cells showed prominent lymphocytic changes, it could be anticipated that mononucleosis-like illnesses or lymphoproliferative disorders would turn out to be manifestations of active HHV-6 infection. In the present study, blood samples from 27 patients previously categorized as having non-Epstein-Barr virus (non-EBV)/noncytomegalovirus (non-CMV) heterophil-negative mononucleosis-like illnesses were tested for IgM and IgG antibodies to HHV-6. Eight of these patients (30%) had serologic evidence of active HHV-6 infection. The clinical spectrum includes a short-lived febrile illness, mild cervical lymphadenopathy, laboratory data suggestive of active viral hepatitis in two patients, and a prolonged febrile illness in a single patient with previously documented positive anti-HIV serology. The viral studies revealed the presence of fourfold HHV-6-specific IgG titer increases by immunofluorescent assay (IFA) in seven serially studied cases and positive IgM serology on one or more samples tested by IFA or enzyme-linked immunosorbent assay (ELISA) in all eight cases. The authors could not determine whether the illnesses represented primary HHV-6 infections in susceptible individuals or reactivation of latent virus. HHV-6 serologic studies may be indicated in patients with mononucleosis-like illnesses with atypical lymphocytosis when EBV and CMV test results are nondiagnostic.
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