Weibel-Palade body Weibel-Palade bodies are specific for vascular endothelium. They have a single membrane, usually a dense interior, and present with rounded, oval or rod-shaped profiles. They possess microtubule-like inclusions which may image as striations in long section, and as small circular profiles in cross section. These inclusions, however, are not true tubulin-containing microtubules. Because of these inclusions and the overall shape of Weibel-Palade bodies, they are also known as rod-shaped (micro)tubulated bodies. They may be identified in better differentiated vascular neoplasms, but are rarely found in more poorly differentiated tumors. Although a specific marker for normal endothelium, Weibel-Palade bodies are of limited diagnostic use in surgical pathology. Occasionally, though, they may be helpful by indicating that the particular cell being studied is not a tumor cell.

Figure 1. A. A vessel in a tumor containing many small dense bodies within endothelial cells on either side of the lumen (L). These are Weibel-Palade bodies although the distinctive internal structure cannot be resolved at this magnification. X20,000. B. Three Weibel-Palade bodies, two in long section (arrows) showing internal microtubular elements. Note pinocytotic vesicles (arrowheads) and basal lamina (BL). X95,000. C. A group of Weibel-Palade bodies, showing circular profiles of transversely sectioned microtubular elements. X66,000.