Desmosomes of epithelial malignant mesothelioma

Morphometric examination of desmosomes by electron microscopy may help distinguish epithelial malignant mesotheliomas (EMM) from adenocarcinomas (AC). The lengths of 225 desmosomes from 10 AC and 296 desmosomes from 12 EMM were measured. The mean desmosome length was not significantly different in the two groups. However, only one desmosome greater than 1-micron length was found among the 225 AC desmosomes, whereas seven such "giant" desmosomes were found among 296 EMM desmosomes (p less than 0.001). These long desmosomes ranged up to 4.2 micron in length and involved 4 of 12 cases of EMM. The longest AC desmosome was 1.34 micron. Thus, it is suggested that giant desmosomes be defined as measuring greater than 1 micron in length and that such desmosomes are found much more commonly in EMM than AC and tend to attain greater lengths in EMM.