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A patient with Cushing's syndrome is described who had a metastatic medullary carcinoma of the thyroid which contained corticotropin-releasing factor. ACTH was found by an immunohistochemical method in the patient's pituitary, but not in the thyroid tumor. This is the second report demonstrating corticotropin-releasing factor in tumor tissue in this syndrome. Wider use of immunohistological methods can help distinguish this variety from other tumors associated with the ectopic ACTH syndrome when bioassays are not available.

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Cellular changes produced by viruses can be readily identified using light microscopy and Papanicolaou stain of a fixed specimen. These findings can then be confirmed by viral culture and/or electron microscopy studies. Human polyomavirus, common in transplant recipients or otherwise immunocompromised patients, is one virus that can be identified using these methods. The following is a case study of a 4-yr-old boy with no known immune impairment who exhibited human papovavirus (polyomavirus) on a routine urine examination. The diagnosis was confirmed by electron microscopy.

Cytogenetic analysis of mixed lymphocyte and epithelial thymoma in a nonmyasthenic female patient revealed deletion of part of the short arm of chromosome 6. To our knowledge, this cytogenetic abnormality in a benign thymoma has not been previously described in the literature, which is reviewed.