In 14 cases of hairy cell leukemia unique vascular lesions not previously reported were observed in surgically resected spleens and hepatic biopsies. In all 14 spleens there were variably prominent distended spaces filled with erythrocytes and resembling dilated sinuses. These structures appeared to be lined by hairy cells,and studies utilizing histochemical and enzymatic methods confirmed that they were in fact pseudosinuses lacking the endothelial cells and ring fibers of normal splenic sinuses. These changes were not present in normal spleens or in spleens involved by other types of chronic leukemia, and appear to be qualitatively specific for hairy cell leukemia. In three of five hepatic biopsies similar angiomatous lesions were present in multifocal clusters resembling hemangiomas. Their pathogenesis may be related to possible adherence of hairy cells to reticulum fibers in involved tissues.

Juvenile laryngeal papillomas, solitary laryngeal papillomas of the adult, and cylindric cell papillomas of the nose and sinuses were examined for the presence of papillomavirus antigens by means of immunocytochemistry. By using an antiserum capable of recognizing a common group antigen that reacts with papillomavirus antigens of different species, it was found that half of the juvenile laryngeal papillomas studied contained cells staining for papillomavirus antigens. No positive cells were found in adult solitary papillomas or cylindric cell papillomas. These results strongly implicate a human papillomavirus as the causative agent of juvenile multiple laryngeal papillomas.

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