Endocrine activity in a large hibernoma.

Light, ultrastructural, biochemical and histochemical analyses of a large hibernoma revealed endocrine-like secretory activity. By biochemical and gas chromatographic analyses, cholesterol and steroid hormones were detected. These findings were confirmed by detection of cortisol and testosterone, radioimmune assay, and immunocytochemical testing. Morphologic evidence of endocrine-like secretory activity was provided by both transmission and scanning electron microscopic examination, which, in addition, revealed unusual features that have not previously been described for hibernomas: 1) "endoplasmacrine" lipid granule secretion, 2) rows of pedunculated or detached plasmalemmal granules in perisinusoidal cells, 3) periodic plasmalemmal densities, which were present also along membrane remnants surrounding lipid granules, and 4) highly innervated interstitial veins with eccentric lumens and peculiar thick muscular coats, which resembled structures seen in humans only in the central vein of the adrenal gland.