The tadpole-shaped structures in human non-necrotizing granulomas.

We scrutinized the secondary lysosomal vesicle of the epitheloid cell from 9 patients whose biopsy specimens show multiple non-necrotizing granulomas by light microscopy (LM). In 4 of the 9 patients, we found tadpole-shaped structures (TSS) approximately tenfold larger than the size of the mycobacteriophage by transmission electron microscopy (TEM). In addition, we used a plasma etching method on epon-embedded tissue and successfully demonstrated the stereoscopic appearance of the TSS by scanning electron microscopy (SEM). The identified TSS were further analyzed with an X-ray energy dispersive spectrometer for their microchemistry. The TSS appeared to be integral structures by TEM and SEM and did not contain any nonbiologic elements when analyzed with the X-ray energy dispersive spectrometer. Their location as well as their morphologic features and microchemistry suggested that the TSS are a microorganism and related to the formation of the granulomas in our 4 patients.