Extracellular matrix globules in renal oncocytoma

Extracellular hyaline globules resulting from abnormal accumulation of matrix components have been described in several pathological conditions, including renal tumors. We studied 16 renal oncocytomas and observed these bodies in 11 of them. In these tumors, they showed a homogeneous texture as well as roundish, smooth contours, and were easily detected in hematoxylin-eosin sections in five cases. PAS staining greatly facilitated the identification of globules in the remaining six cases, where they were fewer in number. Immunohistochemically, they appeared to be composed primarily of basement membrane material, being strongly reactive to antibodies for type IV collagen, laminin, and heparan sulphate proteoglycan. In addition, a weak immunoreactivity for type I and type III collagen, and fibronectin was observed in some cases, whereas no globule stained for tenascin. We also analyzed 89 renal cell carcinomas, and found somewhat similar bodies in 10 of them. However, they were more scanty in the latter tumors, and displayed a more irregular configuration with granular or smudged contours. We conclude that, although the mere presence of extracellular hyaline globules does not justify a distinction between renal oncocytoma and renal cell carcinoma, the detection of a large number of well-demarcated, roundish extracellular bodies with smooth contours suggests renal oncocytoma.