Hyaline globules in Kaposi's sarcoma: a light microscopic and immunohistochemical study

Hyaline globules (HG) were detected in 51 of 54 Kaposi's sarcoma (KS) lesions (94.4%), including all four non-acquired immunodeficiency syndrome (AIDS) cases of cutaneous KS in this group of cases. Thus, there was no correlation between the presence of HG and the presence or absence of AIDS, nor could we demonstrate any relationship between the presence or prominence of HG and either the histologic pattern or anatomical distribution of KS. HG were located mainly in the cytoplasm of perivascular cells, histiocytoid cells, and spindle-shaped cells and occasionally in endothelial cells lining vessels or slit-like spaces. Extracellular HG were also seen. HG stained positively with periodic acid-Schiff with and without diastase digestion and with phosphotungstic acid-hematoxylin. HG were immunohistochemically negative for alpha 1-antitrypsin, alpha 1-antichymotrypsin, lysozyme, and Factor VIII-related antigen, but the cells containing HG were often positive for alpha 1-antichymotrypsin and occasionally for alpha 1-antitrypsin and Factor VIII-related antigen. HG were also detected in five of six angiosarcomas, two of ten pyogenic granulomas, and seven of 32 inflammatory granulation tissues. These were immunohistochemically similar to HG in KS. Thus, HG are not specific for KS. We support the interpretation that HG are most likely digested erythrocytes.