['Prostasomes are small (40-500 nm), granule-like bodies, found in normal epithelial cells of the prostate and secreted into the prostate duct system. Also poorly differentiated prostate cancer cells are producing prostasomes, since we could isolate and purify prostasomes from vertebral metastases with biochemical methods. To find out whether these prostasomes are secreted into extracellular sites of the metastases, we used electron microscopy.', 'Small biopsies from vertebral metastases of prostate cancer, taken directly from the operating field at surgery, were immediately fixated, embedded in plastic and processed for electron microscopy.', 'We found that prostasomes could be identified extracellularly in the interstitial tissues as well as in the cytoplasm of the metastatic cells.'] Are prostasomes secreted from poorly differentiated cells of prostate cancer metastases?