Organic fragmentation in pulmonary thrombo-emboli

Organic fragmentation is a cell-mediated process whereby the periphery of thrombo-emboli is broken up into multiple tiny fragments lined by flat cells and separated by endothelialised clefts and spaces. The process was looked for in 238 lung emboli from 107 subjects and was observed in 45 emboli (41 subjects). The true incidence is much higher since fragmentation is preceded by the surfacing of emboli by flat endothelial cells. Among such emboli its frequency was 41%. Fragmentation can involve emboli of all sizes though it is most frequent and extensive in small ones. The process is important for the resolution of emboli and helps the canalisation of the embolised arteries. It reduces the size of emboli and may also undermine mural attachments and thereby lessen the extent of anchoring to the vessel wall. The mechanism of fragmentation and the origin of the cells responsible are discussed.